UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

Commission File Number 1-8022

CSX Corporation

(Exact name of registrant as specified in its charter)

(904) 359-3200

(Registrant’s telephone number, including area code)

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

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

None

      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.     Yes þ          No o

      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 the 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.     þ

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

      On June 25, 2004, the aggregate market value of the Registrant’s voting stock held by non-affiliates was approximately $7.0 billion (based on the New York Stock Exchange closing price on such date).

      On February 28, 2005, there were 215,619,764 shares of Common Stock outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

      Portions of the Registrant’s Definitive Proxy Statement (“the Proxy Statement”) to be filed with respect to its annual meeting of shareholders scheduled to be held on May 4, 2005.

CSX CORPORATION

FORM 10-K

TABLE OF CONTENTS

PART I

      CSX Corporation (“CSX” or the “Company”) operates one of the largest rail networks in the United States and also arranges for and provides integrated rail and truck (“intermodal”) transportation services across the United States and key markets in Canada and Mexico. Its marine operations, described below under the caption “Discontinued Operations,” included an international terminal services company, which operated and developed container terminals, distribution facilities and related terminal activities. CSX also owns and operates the Greenbrier, a AAA Five-Diamond resort located in White Sulphur Springs, West Virginia.

Surface Transportation

      Headquartered in Jacksonville, Florida, CSX Transportation Inc. (“CSXT”) is the largest rail network in the eastern United States, providing rail freight transportation over a network of more than 22,000 route miles in 23 states, the District of Columbia and two Canadian provinces.

      CSX Intermodal Inc. (“CSXI”) is one of the nation’s largest transcontinental intermodal transportation service providers, operating a network of dedicated intermodal facilities across North America. Headquartered in Jacksonville, Florida, the CSXI network handles approximately 500 dedicated trains among its 44 terminals weekly.

      The rail and intermodal segments are viewed on a combined basis as Surface Transportation operations.

Discontinued Operations

      CSX World Terminals, LLC (“CSXWT”) operates container-freight terminal facilities in Asia, Europe, Australia, Latin America and the United States. CSXWT is headquartered in Charlotte, North Carolina.

      On February 22, 2005 CSX sold its International Terminals business through the sale of all of the issued and outstanding shares of capital stock of SL Service, Inc. (“SLSI”), and all of its interest in Orange Blossom Investment Company, Ltd. to Dubai Ports International FZE (“DPI”) for closing cash consideration of $1.142 billion, subject to final working capital and long-term debt adjustments. As a result of the sale CSX will recognize a pretax gain in the first quarter of 2005 and expects to tender substantial tax payments triggered by the transaction beginning in the second quarter of 2005. Of the gross proceeds, approximately $115 million is allocated for the purchase of a minority interest in an International Terminals’ subsidiary, acquired in the first quarter of 2005 and divested as part of the sale to DPI. Approximately $100 million was paid for this interest subsequent to December 31, 2004, with the final payment expected in the first quarter of 2005. The Company is considering options regarding the use of net cash proceeds including reduction of debt and other corporate purposes.

      SLSI also holds certain residual assets and liabilities as a result of prior divestitures and discontinuances. A wholly-owned subsidiary of CSX retains the rights to those assets and indemnifies DPI, SLSI and related entities against those liabilities pursuant to a separate agreement. CSX guarantees the obligations of its subsidiary under this separate agreement.

      Consequently, the results of operations and financial position of the Company’s International Terminals business are reported as Discontinued Operations for all periods presented.

Divestitures

      In February 2003, CSX conveyed most of its interest in its domestic container-shipping subsidiary, CSX Lines LLC (“CSX Lines”), to a new venture formed with The Carlyle Group for approximately $300 million (gross cash proceeds of approximately $240 million, $214 million net of transaction costs, and $60 million of securities). CSX Lines was subsequently renamed Horizon Lines LLC (“Horizon”). Horizon subleased vessels and equipment from certain affiliates of CSX covering the primary financial obligations related to $265 million of leases under which CSX or one of its affiliates will remain a lessee/ sublessor or guarantor. A deferred pretax gain of approximately $127 million as a result of the transaction is being recognized over the 12-year sub-lease term. The securities contained a term of 7 years and a preferred return feature. During the third quarter of 2003, CSX received a $15 million payment from Horizon Lines, which included $3 million of interest, in return of a portion of its investment in Horizon. The investing section of the 2003 Consolidated Statement of Cash Flows includes proceeds from divestiture of $226 million and $3 million of interest on investment is included in net earnings.

      In July 2004, Horizon was acquired by an unrelated third party, and CSX received $59 million, which included $48 million for the purchase of its ownership interest in Horizon, $4 million of interest, and a performance payment of $7 million, which will also be recognized over the 12-year sub-lease term. The investing section of the 2004 Consolidated Statement of Cash Flows includes proceeds from divestiture of $55 million and $4 million of interest on investment is included in net earnings. However, CSX and one of its affiliates will continue to remain a lessee/ sublessor or guarantor on certain vessels and equipment as long as the subleases remain in effect. (See Note 19, Commitments and Contingencies.)

Financial Information about Operating Segments

      See Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations for operating revenue, operating income and total assets by segment for each of the last three fiscal years.

General

      The Company makes available free of charge through its website at www.csx.com, its annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K, and all amendments thereto, as soon as reasonably practicable after such reports are filed with or furnished to the Securities and Exchange Commission.

      CSX has included the CEO and CFO certifications regarding the Company’s public disclosure required by Section 302 of the Sarbanes-Oxley Act of 2002 as Exhibits 31(a) and (b) to this report. Additionally, CSX filed with the NYSE the CEO’s certification regarding the Company’s compliance with the NYSE’s Corporate Governance Listing Standards (Listing Standards) pursuant to Section 303A.12(a) of the Listing Standards, which was dated June 2, 2004, and indicated that the CEO was not aware of any violations of the Listing Standards by the Corporation.

      For additional information concerning business conducted by CSX during 2004, see Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations and Item 8. Financial Statements and Supplementary Data — Note 20, Business Segments.

Employees

      The information set forth in Item 6. Selected Financial Data is incorporated herein by reference.

      The information set forth in the following sections is incorporated herein by reference:

      CSX is involved in routine litigation incidental to its business and is a party to a number of legal actions and claims, various governmental proceedings and private civil lawsuits, including those related to environmental matters, Federal Employers’ Liability Act claims by employees, other personal injury claims, and disputes and complaints involving certain transportation rates and charges. Some of the legal proceedings include claims for compensatory as well as punitive damages, and others purport to be class actions. While the final outcome of these matters cannot be predicted with certainty, considering among other things the meritorious legal defenses available and liabilities that have been recorded along with applicable insurance, it is the opinion of CSX management that none of these items will have a material adverse effect on the results of operations, financial position or liquidity of CSX. However, an unexpected adverse resolution of one or more of these items could have a material adverse effect on the results of operations in a particular quarter or fiscal year. The Company is also party to a number of actions, the resolution of which could result in gain realization in amounts that could be material to results of operations in the quarters received.

      See Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations under the caption “Critical Accounting Estimates, Casualty, Environmental and Legal Reserves.”

      There were no matters submitted to a vote of security holders in the fourth quarter of 2004.

Executive Officers of the Registrant

      Executive officers of CSX are elected by the CSX Board of Directors and generally hold office until the next annual election of officers. Officers of CSX business units are elected annually by the respective Boards of Directors of the business units. There are no family relationships or any

arrangement or understanding between any officer and any other person pursuant to which such officer was selected. Effective March 1, 2005, the executive officers will be as follows:

PART II

Market Information

      CSX’s common stock is listed on the New York and Swiss stock exchanges and trades with unlisted privileges on the Midwest, Boston, Cincinnati, Pacific and Philadelphia stock exchanges. The official trading symbol is “CSX.” In 2004, the Company decided to delist its common stock from the London Stock Exchange, effective December 31, 2004, due to low trading volume and costs associated with listing maintenance.

Description of Common and Preferred Stocks

      A total of 300 million shares of common stock is authorized, of which 215,528,753 shares were outstanding as of December 31, 2004. Each share is entitled to one vote in all matters requiring a vote of shareholders. There are no pre-emptive rights. At February 28, 2005, there were 70,398 common stock shareholders of record.

      A total of 25 million shares of preferred stock is authorized, none of which is currently outstanding.

Equity Compensation Plan Information

      The following table summarizes the equity compensation plans under which CSX common stock may be issued as of December 31, 2004.

      The following table sets forth, for the quarters indicated, the dividends declared and the high and low sales prices of the Company’s common stock.

See accompanying Consolidated Financial Statements

Significant events include the following:

      The following discussion should be read in conjunction with Item 8. Financial Statements and Supplementary Data and other information included in this report. CSX follows a 52/53 week fiscal reporting calendar. Fiscal year 2004 consisted of a 53-week year ending on December 31, 2004. Fiscal year 2003 consisted of 52 weeks ending on December 26, 2003.

EXECUTIVE SUMMARY

2004 Surface Transportation Highlights and Challenges

Revenue

      Revenue increased by 8% or $581 million year-over-year, a portion of which is due to 53 weeks instead of 52 weeks in the fiscal year ended December 31, 2004. The fourth quarter of 2004 marked the 11th consecutive quarter of year-over-year revenue growth. Increased demand for coal was a primary driver of the revenue growth due to both increased electricity generation and rebuilding utility stockpile inventory. In addition, demand created from a generally strong industrial economy propelled all merchandise markets and CSXI to record revenue levels. All major markets showed year-over-year improvement in revenue-per-car due to continued yield management strategies and the Company’s fuel surcharge program.

Volume

      Volume growth during 2004 lagged others in the rail industry due to service related constraints at CSXT and the Network Simplification Initiative (“NSI”) at CSXI. Several markets exhibited potential for additional volume especially within the coal and metals markets, if the Company’s car fleet utilization had improved. Furthermore, some customers diverted traffic to other rail carriers or other modes of transportation due to service challenges.

      In July, CSXI implemented NSI, which eliminated 26 weekly train starts, in an effort to improve overall contributions by consolidating volumes on fewer trains. The annualized impact from NSI is estimated to be increase CSXI’s operating income by $8 million or approximately 5%.

Fuel Costs and Fuel Surcharge Program

      Fuel expenses increased 16% to $656 million in 2004, net of $63 million of fuel hedging benefits, from $566 million in 2003 due principally to the rising price per gallon of diesel fuel. Fuel hedging activity had no impact on fuel expense for the fiscal year ended December 26, 2003. The average price per gallon of diesel fuel, including benefits from CSX’s fuel hedging program, was $1.0950 in 2004 versus $0.9564 in 2003. In addition, the fuel surcharge programs within the Surface Transportation business segment and contractual cost escalation clauses used in most multi-year customer contracts partially offset fuel cost increases.

Operations

      Fiscal year 2004 proved to be operationally challenging. As illustrated in the table below, key measures of network performance declined versus prior year and had an adverse impact on service

consistency, expenses and CSX’s ability to fully capture growth opportunities during a period of high demand for transportation services.

RAIL OPERATING STATISTICS(a)

(a) Amounts for 2004 are estimated.

Implementation of the ONE Plan

      The ONE Plan was a major initiative launched across the CSX network in the third quarter of 2004 aimed at improving network performance. The first phase of the ONE Plan included a complete redesign of the operating plan for automotive and merchandise shipments to improve service consistency and efficiency by reducing terminal handlings and routing miles. With the new operating plan in place, management focused on consistent execution and refining the plan in response to changing shipment volumes and flows. Early results were promising, with key measures improving sequentially from the third to the fourth quarter of 2004.

Expenses

      CSX follows a 52/53 week fiscal reporting calendar. Fiscal year 2004 consisted of a 53-week year ending on December 31, 2004. Fiscal year 2003 consisted of 52 weeks ending on December 26, 2003.