UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

Commission File Number 0-10436

L. B. FOSTER COMPANY

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code:

(412) 928-3417

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

Common Stock, Par Value $0.01.

      Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports) and (2) has been subject to such filing requirements for the past 90 days.     þ Yes          o No

      Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this form 10-K.     o

      Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Act). þ Yes o No

      The aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, as of the last business day of the registrant’s most recently completed second fiscal quarter was $76,584,384.

      Indicate the number of shares outstanding of each one of the registrant’s classes of common stock as of the latest practicable date.

      Documents Incorporated by Reference:

      Portions of the Proxy Statement prepared for the 2005 annual meeting of stockholders are incorporated by reference in Items 10, 11, 12 and 14 of Part III.

TABLE OF CONTENTS

PART I

Summary Description of Businesses

      L. B. Foster Company is engaged in the manufacture, fabrication and distribution of products that serve the nation’s surface transportation infrastructure. As used herein, “Foster” or the “Company” means L. B. Foster Company and its divisions and subsidiaries, unless the context otherwise requires.

      For rail markets, Foster provides a full line of new and used rail, trackwork, and accessories to railroads, mines and industry. The Company also designs and produces concrete railroad ties, insulated rail joints, power rail, track fasteners, coverboards and special accessories for mass transit and other rail systems worldwide.

      For the construction industry, the Company sells steel sheet, H-bearing and pipe piling and rents steel sheet piling for foundation and earth retention requirements. In addition, Foster supplies fabricated structural steel, bridge decking, bridge railing, expansion joints, mechanically stabilized earth wall systems, precast concrete buildings and other products for highway construction and repair.

      For tubular markets, the Company supplies pipe coatings for natural gas pipelines and utilities. The Company also produces threaded pipe products for industrial water well and irrigation markets.

      The Company classifies its activities into three business segments: Rail products, Construction products, and Tubular products. Financial information concerning the segments is set forth in Item 8, Note 19. The following table shows for the last three fiscal years the net sales generated by each of the current business segments as a percentage of total net sales.

RAIL PRODUCTS

      L. B. Foster Company’s rail products include heavy and light rail, relay rail, concrete ties, insulated rail joints, rail accessories and transit products. The Company is a major rail products supplier to industrial plants, contractors, railroads, mines and mass transit systems.

      The Company sells heavy rail mainly to transit authorities, industrial companies, and rail contractors for railroad sidings, plant trackage, and other carrier and material handling applications. Additionally, the Company makes some sales of heavy rail to railroad companies and to foreign buyers. The Company sells light rail for mining and material handling applications.

      Rail accessories include trackwork, ties, track spikes, bolts, angle bars and other products required to install or maintain rail lines. These products are sold to railroads, rail contractors and industrial customers and are manufactured within the Company or purchased from other manufacturers.

      The Company’s Allegheny Rail Products (ARP) division engineers and markets insulated rail joints and related accessories for the railroad and mass transit industries. Insulated joints are made in-house and subcontracted.

      The Company’s Transit Products division supplies power rail, direct fixation fasteners, coverboards and special accessories primarily for mass transit systems. Most of these products are manufactured by subcontractors and are usually sold by sealed bid to transit authorities or to rail contractors, worldwide.

      The Company’s Trackwork division sells new and used rail, rail accessories, and produces trackwork for industrial markets.

      The Company’s CXT subsidiary manufactures engineered concrete railroad ties for the railroad and transit industries.

      The Company’s Rail Technologies subsidiary developed rail signaling and communications devices for North American railroads. On December 31, 2002, this business was reclassified as a discontinued operation and was sold in February 2003.

CONSTRUCTION PRODUCTS

      L. B. Foster Company’s construction products consist of sheet, pipe and bearing piling, fabricated highway products, and precast concrete buildings.

      Sheet piling products are interlocking structural steel sections that are generally used to provide lateral support at construction sites. Bearing piling products are steel H-beam sections which, in their principal use, are driven into the ground for support of structures such as bridge piers and high-rise buildings. Sheet piling is sold or leased and bearing piling is sold principally to contractors and construction companies.

      Other construction products consist of precast concrete buildings, sold principally to national and state parks, and fabricated highway products. Fabricated highway products consist principally of fabricated structural steel, bridge decking, aluminum and steel bridge rail and other steel products, which are fabricated by the Company, as well as mechanically stabilized earth wall systems. The major purchasers of these products are contractors for state, municipal and other governmental projects.

      Sales of the Company’s construction products are partly dependent upon the level of activity in the construction industry. Accordingly, sales of these products have traditionally been somewhat higher during the second and third quarters than during the first and fourth quarters of each year.

TUBULAR PRODUCTS

      The Company provides fusion bond epoxy and other coatings for corrosion protection on oil, gas and other pipelines. The Company also supplies special pipe products such as water well casing, column pipe, couplings, and related products for agricultural, municipal and industrial water wells, as well as micropiles for construction foundation repair and slope stabilization.

MARKETING AND COMPETITION

      L. B. Foster Company generally markets its rail, construction and tubular products directly in all major industrial areas of the United States through a national sales force of 72 employees, including outside sales, inside sales, and customer service representatives. The Company maintains 17 sales offices and 14 warehouse, plant and yard facilities throughout the country. During 2004, approximately 5% of the Company’s total sales were for export.

      The major markets for the Company’s products are highly competitive. Product availability, quality, service and price are principal factors of competition within each of these markets. No other company provides the same product mix to the various markets the Company serves. The Company faces significant competition from different groups of companies in each product line.

RAW MATERIALS AND SUPPLIES

      Most of the Company’s inventory is purchased in the form of finished or semi-finished product. With the exception of relay rail which is purchased from railroads or rail take-up contractors, the Company purchases most of its inventory from domestic and foreign steel producers. There are few domestic suppliers of new rail products and the Company could be adversely affected if a domestic supplier ceased making such material available to the Company. Additionally, the Company has an agreement with a steel mill to distribute steel

sheet piling and H-bearing pile in North America. See Note 18 to the consolidated financial statements for additional information on this matter.

      The Company’s purchases from foreign suppliers are subject to the usual risks associated with changes in international conditions and to United States laws which could impose import restrictions on selected classes of products and anti-dumping duties if products are sold in the United States below certain prices.

BACKLOG

      The dollar amount of firm, unfilled customer orders at December 31, 2004 and 2003 by segment follows:

      Approximately 11% of the December 31, 2004 backlog is related to projects that will extend beyond 2005.

RESEARCH AND DEVELOPMENT

      The Company’s expenditures for research and development are not material.

ENVIRONMENTAL DISCLOSURES

      While it is not possible to quantify with certainty the potential impact of actions regarding environmental matters, particularly for future remediation and other compliance efforts, in the opinion of management, compliance with environmental protection laws will not have a material adverse effect on the financial condition, competitive position, or capital expenditures of the Company. However, the Company’s efforts to comply with stringent environmental regulations may have an adverse effect on the Company’s future earnings.

EMPLOYEES AND EMPLOYEE RELATIONS

      The Company has 621 employees, of whom 365 are hourly production workers and 256 are salaried employees. Approximately 150 of the hourly paid employees are represented by unions. The union contract at the Company’s Bedford, PA fabricated products facility expired on March 10, 2005. The employees are continuing to work under the terms of the expired contract while negotiations continue. The Company believes it can successfully negotiate an extension to the contract without a work stoppage. The Company has not suffered any major work stoppages during the past five years and considers its relations with its employees to be satisfactory.

      Substantially all of the Company’s hourly paid employees are covered by one of the Company’s noncontributory, defined benefit plans or defined contribution plan. Substantially all of the Company’s salaried employees are covered by a defined contribution plan.

      The location and general description of the principal properties which are owned or leased by L. B. Foster Company, together with the segment of the Company’s business using the properties, are set forth in the following table:

      Including the properties listed above, the Company has 17 sales offices and 14 warehouse, plant and yard facilities located throughout the country. The Company’s facilities are in good condition. During 2005, the Company plans to build a new concrete tie facility in Tucson, AZ in order to maintain adequate production facilities for its present and foreseeable future.

      In 2004, the operations at the Doraville, GA location which consisted of transit products operations and yard storage moved to a leased facility in Suwanee, GA. The Doraville, GA location is currently being rented and the Company is preparing the property for sale. At December 31, 2004, the property did not meet the criteria to be classified as “held for resale” under Statement of Financial Accounting Standard No. 144, “Accounting for the Impairment or Disposal of Long-Lived Assets” and thus, continues to be classified as held and used.

      In 2000, the Company’s subsidiary sold concrete railroad crossing panels to a general contractor on a Texas transit project. Due to a variety of factors, including deficiencies in the owner’s project specifications, the panels have deteriorated and the owner either has replaced or is in the process of replacing these panels. The general contractor and the owner are currently engaged in dispute resolution procedures, which probably will continue through the second quarter of 2005. The general contractor has notified the Company that, depending on the outcome of these proceedings, it may file a suit against the Company’s subsidiary. Although no assurances can be given, the Company believes that it has meritorious defenses to such claims and will vigorously defend against such a suit.

      In the second quarter of 2004, a gas company filed a complaint against the Company in Allegheny County, PA, alleging that in 1989 the Company had applied epoxy coating on 25,000 feet of pipe and that, as a result of inadequate surface preparation of the pipe, the coating had blistered and deteriorated. The Company does not believe that the gas company’s alleged problems are the Company’s responsibility. Although no assurances can be given, the Company believes that it has meritorious defenses to such claims and will vigorously defend against such a suit.

      Another gas company filed suit against the Company in August, 2004, in Erie County, NY, alleging that pipe coating which the Company furnished in 1989 had deteriorated and that the gas supply company had incurred $1,000,000 in damages. The Company does not, however, believe that the gas supply company’s alleged problem is the Company’s responsibility. Although no assurances can be given, the Company believes that it has meritorious defenses to such claims and will vigorously defend against such a suit.

      None.

      Information concerning the executive officers of the Company is set forth below. With respect to the period prior to August 18, 1977, references to the Company are to the Company’s predecessor, Foster Industries, Inc.

      Mr. Lee Foster has been a director of the Company since 1990 and he has been Chairman of the Board since 1998. He was the Chief Executive Officer of the Company from May 1990 until January 2002.

      Mr. Hasselbusch has been Chief Executive Officer and a director of the Company since January 2002, and President of the Company since March 2000. He served as Vice President — Construction and Tubular Products from December 1996 to December 1998 and as Chief Operating Officer from January 1999 until he was named Chief Executive Officer in January 2002.

      Mr. Bloem was elected Senior Vice President — Concrete Products in March 2000, having previously served as Vice President — Geotechnical and Precast Division from October 1999, and President — Geotechnical Division from August 1998. Prior to joining the Company in August 1998, Mr. Bloem served as Vice President — VSL Corporation.

      Ms. Brumbaugh was elected Vice President — Tubular Products in November 2004, having previously served as General Manager, Coated Products since 1996. Ms. Brumbaugh has served in various capacities with the Company since her initial employment in 1980.

      Mr. Fisher was elected Senior Vice President — Rail in October 2002, having previously served as Senior Vice President — Product Management since June 2000. From October 1997 until June 2000, Mr. Fisher served as Vice President — Rail Procurement. Prior to October 1997, Mr. Fisher served in various other capacities with the Company since his employment in 1977.

      Mr. Donald Foster was elected Senior Vice President — Construction Products in February 2005, having served as Vice President — Piling Products since November 2004, and General Manager of Piling since September, 2004. Prior to joining the Company, Mr. Foster was President of Metalsbridge, a financed supply chain logistics entity. He served U.S. Steel Corporation as an Officer from 1999 to 2003. During that time, Mr. Foster functioned as Vice President International, President of UEC Technologies and President, United States Steel International, Inc. Joining U.S. Steel Corporation in 1979, he served in a number of general management roles in the distribution and construction markets.

      Mr. Howard was elected Vice President — Human Resources in June 2002. Mr. Howard was Vice President — Human Resources of Bombardier Transportation, the former Daimler Chrysler Rail Systems, a supplier of rail vehicles, transportation systems and services, worldwide, from January 1992 until June 2002. Mr. Howard also served as Director of Employee Relations with US Airways from 1981 until 1992.

      Mr. Kasel was elected Vice President — Operations and Manufacturing in April 2003. Mr. Kasel served as Vice President of Operations for Mammoth, Inc., a Nortek company from 2000 to 2003. His career also included General Manager of Robertshaw Controls and Operations Manager of Shizuki America prior to 2000.

      Mr. Lippard was elected Vice President — Rail Product Sales in June 2000. Prior to re-joining the Company in 2000, Mr. Lippard served as Vice President — International Trading for Tube City, Inc. from June 1998. Mr. Lippard served in various other capacities with the Company since his initial employment in 1991.

      Ms. Patterson was elected Controller in February 1999, having previously served as Assistant Controller since May 1997 and Manager of Accounting since March 1988. Prior to March 1988, Ms. Patterson served in various other capacities with the Company since her employment in 1977.

      Mr. Russo was elected Senior Vice President, Chief Financial Officer and Treasurer in December 2002, having previously served as Vice President and Chief Financial Officer since July 2002. Mr. Russo was Corporate Controller of WESCO International Inc., a distributor of electrical construction products, electrical and industrial MRO supplies and integrated supply services, from 1999 until joining the Company in 2002. Mr. Russo also served as Corporate Controller of Life Fitness Inc., an international designer, manufacturer and distributor of aerobic and strength training fitness equipment, primarily to the commercial marketplace (health clubs), from 1991 until 1998.

      Mr. Voltz was elected Vice President, General Counsel and Secretary in December 1987. Mr. Voltz joined the Company in 1981.

      Mr. Walsh was elected Vice President — Fabricated Products in February 2001. Prior to joining the Company in February 2001, Mr. Walsh served as General Manager of IKG-Greulich, a business unit of Harsco Corp., from February 1998, and as Vice President of Harris Specialty Chemicals Inc. from January 1995.

      Officers are elected annually at the organizational meeting of the Board of Directors following the annual meeting of stockholders.

Code of Ethics

      L. B. Foster Company maintains a code of ethics applicable to all directors and employees, including its Chief Executive Officer, Chief Financial Officer and Controller. The code of ethics is posted on the Company’s website, www.lbfoster.com. The Company intends to satisfy the disclosure requirement regarding certain amendments to, or waivers from, provisions of its code of ethics by posting such information on the Company’s website.

PART II

Stock Market Information

      The Company had 695 common shareholders of record on January 31, 2005. Common stock prices are quoted daily through the National Association of Security Dealers, Inc. in its over-the-counter NASDAQ quotation service (Symbol FSTR). The quarterly high and low bid price quotations for common shares (which represent prices between broker-dealers and do not include markup, markdown or commission and may not necessarily represent actual transactions) follow:

Dividends

      No cash dividends were paid on the Company’s Common stock during 2004 and 2003, and the Company has no plan to pay dividends in the foreseeable future. The Company’s ability to pay cash dividends is limited by its revolving credit agreement.

Securities Authorized for Issuance Under Equity Compensation Plans

      The following table sets forth information as of December 31, 2004 with respect to compensation plans under which equity securities of the Company are authorized for issuance.

      The Company awarded shares of its common stock to its outside directors on a biannual basis from June 2000 through January 2003 under an arrangement not approved by the Company’s shareholders. A total of 22,984 shares of common stock was so awarded and this program has been terminated. At the Company’s 2003 Annual Shareholders’ Meeting, a new plan was approved by the Company’s shareholders under which outside directors receive 2,500 shares of the Company’s common stock at each annual shareholder meeting at which such outside director is elected or re-elected, commencing with the Company’s 2003 Annual Shareholders’ Meeting. Through 2004, there have been 20,000 shares issued under this plan.

      The Company’s Board of Directors has authorized the purchase of up to 1,500,000 shares of its Common stock at prevailing market prices. No purchases have been made since the first quarter of 2001. From August 1997 through March 2001, the Company repurchased 973,398 shares at a cost of approximately $5.0 million.

The timing and extent of future purchases will depend on market conditions and options available to the Company for alternate financing sources.