Exhibit 99.1

NEWS RELEASE

FOR IMMEDIATE RELEASE

Pacific Continental Corporation Reports Record Quarterly Loan Growth

Continued balance sheet expansion and earnings growth provide solid momentum toward merger with Columbia Bank

EUGENE, Ore., April 27, 2017 – Pacific Continental Corporation (Nasdaq: PCBK), the holding company of Pacific Continental Bank, today reported financial results for the first quarter ended March 31, 2017.

First Quarter 2017 Highlights:

Merger Update

On January 9, 2017, Pacific Continental Corporation entered into a definitive agreement to merge with Columbia Banking System, Inc., headquartered in Tacoma, Washington. Upon completion of the merger, the combined company will operate under the Columbia Bank name and brand. The agreement was approved by the Board of Directors of each company. Closing of the transaction, which is currently expected to occur in mid-2017, is contingent on shareholder approval and receipt of necessary regulatory approvals, along with satisfaction of other customary closing conditions.

Net Income Highlights

Net income for the first quarter 2017 was $6.6 million, or $0.29 per diluted share. Included in our net income were non-core costs associated with our pending merger with Columbia Bank of approximately $933 thousand, or approximately $0.03 per diluted share. The provision for loan losses expense in the first quarter 2017 was $900 thousand, compared to $1.9 million for the fourth quarter 2016. Annualized returns on average assets, average equity and average tangible equity for first quarter 2017 were 1.03%, 9.63%, and 12.93%, respectively, compared to 1.08%, 9.93%, and 13.35% for fourth quarter 2016.

“Our entire team did an outstanding job in the first quarter”, said Roger Busse, chief executive officer. “For our team to produce record quarterly loan growth during the period in which we announced our merger with Columbia Bank is truly remarkable. I couldn’t be more proud of our lenders, support staff and entire organization.”

First quarter 2017 noninterest income was $2.2 million, a decrease of $191 thousand from the fourth quarter 2016. The decrease relates primarily to lower service charge income, which decreased by $83 thousand. Fourth quarter service charges are typically higher due to annual fees that are charged during the fourth quarter. Additionally, during the fourth quarter, we recognized $327 thousand of gains from the termination of cash flow hedges associated with short term FHLB borrowings.

Noninterest expense for the first quarter 2017 was $15.5 million, which represented a decrease of $365 thousand from the fourth quarter of 2016. Costs associated with merger and acquisition (“M&A”) transactions were $933 thousand during the first quarter 2017, a reduction of $256 thousand from the fourth quarter 2016. M&A related costs incurred during the first quarter related to the pending merger transaction with Columbia Bank, while the fourth quarter costs related our acquisition of Foundation Bank. “Other” expenses were lower by $610 thousand, related primarily to a

reduction of $415 thousand in city and county business taxes. During the fourth quarter 2016, we made a one-time true up payment related to our tax liability associated with the increased presence in Portland and Multnomah County during 2016. The tax payment was calculated based on deposit totals inside the city of Portland and Multnomah County.

Offsetting our expense decreases was an increase of $666 thousand in our salaries and benefits categories. The majority of the increase related to higher payroll taxes, which is typical during the first quarter when FICA limits reset, and lower loan origination costs, which represent an offset to salary expense.

Net Interest Margin

The first quarter 2017 net interest margin was 4.23%, a decrease of 15 basis points from the fourth quarter 2016. The change related to lower acquired loan accretion income, which was $1.3 million for the first quarter 2017 compared to $2.2 million for the fourth quarter 2016. The reduction in accretion income reduced our net interest margin by 16 basis points. As of March 31, 2017, there was $10.0 million fair value discount remaining on acquired loan portfolios. Accretion of loan fair value discounts, excluding any prepayments, are expected to add a minimum of $900 thousand in interest income during the second quarter of 2017, which would improve our margin by approximately 15 basis points. Monthly accretion is accounted for in accordance with GAAP with the majority using the interest-method. However, prepayment or refinancing can accelerate monthly expected accretion income.

The core net interest margin, which removes nonrecurring items and accretion of loan fair value marks, was 4.01% for the first quarter 2017 compared to 3.96% for the fourth quarter 2016. The positive change related primarily to improved yields on our securities portfolio. An outline of our core and reported net interest margins is as follows:

Balance Sheet Highlights

Gross loans grew by $54.9 million in the first quarter 2017, and totaled $1.91 billion at March 31, 2017. Our first quarter 2017 loan growth represents a record for an individual quarter. Growth came especially in the Eugene and Portland markets, as well as in the national health care portfolio. At March 31, 2017, loans to dental practitioners totaled $382.9 million and represented 20.0% of the loan portfolio. This represented an increase of $5.4 million over fourth quarter 2016, when loans to dental practitioners represented 20.3% of the loan portfolio.

Period-end Company-defined core deposits at March 31, 2017, were $1.97 billion, a decrease of $67.8 million from the fourth quarter 2016. The majority of the decrease related primarily to four large deposit clients. One of the clients is a foundation, which saw a large deposit balance increase during the fourth quarter as donations came in for a special project. A large portion, of those funds, approximately $29 million, were withdrawn during the first quarter. The other clients saw seasonal deposit fluctuations in their business accounts, as is typical during the first half of the year.

“Our first quarter loan growth was outstanding and I’m extremely proud of our dedicated team of bankers”, said Casey Hogan, chief operating officer. “While deposits declined, most of that was expected. Additionally, we are not seeing as much new business due to the merger announcement, where we typically find that new deposit prospects will wait until after the merger closes before moving over new business.”

Asset Quality

As of March 31, 2017, the allowance for loan losses as a percentage of outstanding loans was 1.18%, a decrease from the 1.21% reported at December 31, 2016. At March 31, 2017, the allowance for loan losses as a percentage of nonperforming loans, net of government guarantees, increased to 298.86% from 236.88.% at December 31, 2016. During the first quarter 2017, the Company recorded net charge-offs of $742 thousand, compared to net loan recoveries of $48 thousand during the fourth quarter 2016. During the first quarter 2017, the Company made a $900 thousand provision for loan losses compared to a $1.9 million provision in the fourth quarter 2016.

At March 31, 2017, nonperforming assets, net of government guarantees, totaled $18.6 million, or 0.72% of total assets, compared to $21.6 million, or 0.85% of total assets, at December 31, 2016. Nonperforming assets at March 31, 2017, were comprised of $7.6 million of nonperforming loans, net of government guarantees of $2.3 million, and $11.1 million in other real estate owned. Loans past-due 30-89 days were 0.06% of total loans at March 31, 2017, equal to the 0.06% of total loans reported at December 31, 2016. There were no loans over 90 days past due at March 31, 2017 or December 31, 2016.

Capital Adequacy

The Company’s consolidated capital ratios continued to be above the minimum thresholds for the FDIC’s “well- capitalized” designation. At March 31, 2017, the Company’s capital amounts and ratios were as follows:

Non-GAAP Financial Measures

In addition to results presented in accordance with generally accepted accounting principles (GAAP), this press release contains certain non-GAAP financial measures. The Company believes that such non-GAAP financial measures provide investors with information useful in understanding the Company’s financial performance; however, readers of this release are urged to review these non-GAAP financial measures in conjunction with the GAAP results as reported.

Certain financial measures, such as tangible shareholders’ equity, and tangible assets, are considered non-GAAP measures. Management believes including non-GAAP measures along with GAAP measures provides investors with a broader understanding of capital adequacy, funding sources and revenue trends. Tangible shareholders’ equity is calculated as total shareholders’ equity less goodwill and core deposit intangible assets. Additionally, tangible assets are calculated as total assets less goodwill and core deposit intangible assets.

The following table presents a reconciliation of ending total shareholders’ equity (GAAP) to ending tangible shareholders’ equity (non-GAAP), and total assets (GAAP) to total tangible assets (non-GAAP):

About Pacific Continental Bank

Pacific Continental Bank, the wholly-owned operating subsidiary of Pacific Continental Corporation, delivers highly personalized services through fifteen banking offices in Oregon and Washington. The Bank also operates loan production offices in Tacoma, Washington and Denver, Colorado. Pacific Continental, with more than $2.5 billion in assets, has established one of the most unique and attractive metropolitan branch networks in the Pacific Northwest with offices in three of the region’s largest markets, including Seattle, Portland and Eugene. Pacific Continental targets the banking needs of community-based businesses, health care professionals, professional service providers and nonprofit organizations.

Since its founding in 1972, Pacific Continental Bank has been honored with numerous awards and recognitions from highly regarded third-party organizations including The Seattle Times, the Portland Business Journal, the Seattle Business magazine and Oregon Business magazine. A complete list of the company’s awards and recognitions – as well as supplementary information about Pacific Continental Bank – can be found online at www.therightbank.com. Pacific Continental Corporation’s shares are listed on the Nasdaq Global Select Market under the symbol “PCBK” and are a component of the Russell 2000 Index.

Forward-Looking Statement Safe Harbor

This release contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995 (“PSLRA”). All statements other than statements of historical fact are forward looking statements. Forward- looking statements often use words such as “anticipates,” “targets,” “expects,” “estimates,” “intends,” “plans,” “goals,” “believes” and other similar expressions or future or conditional verbs such as “will,” “should,” “would” and “could.” The forward-looking statements made represent Pacific Continental’s current estimates, projections, expectations,

plans or forecasts of its future results and revenues, including but not limited to statements about performance, loan or deposit growth, accretion of loan fair value discount and its expected impact on interest income and core margin, and the benefits of the business combination transaction involving Pacific Continental and Columbia, including the potential for and timing of new deposit and other business, future financial and operating results, and the combined company’s plans, objectives and expectations. These statements are not guarantees of future results or performance and involve certain risks, uncertainties and assumptions that are difficult to predict and are often beyond Pacific Continental’s control. Actual outcomes and results may differ materially from those expressed in, or implied by, any of these forward-looking statements. You should not place undue reliance on any forward-looking statement and should consider all of the following uncertainties and risks, as well as those more fully discussed under “Risk Factors”, “Business”, and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in Pacific Continental’s and Columbia’s most recent Annual Report on Form 10-K, Quarterly Report on Form 10-Q, and in any of Pacific Continental’s and Columbia’s subsequent SEC filings, including the high concentration of loans of the Company’s banking subsidiary in commercial and residential real estate lending and in loans to dental professionals; adverse economic trends in the United States and the markets we serve affecting the Bank’s borrower base; continued erosion or sustained low levels of consumer confidence; changes in the Federal Reserve’s monetary policies and the regulatory environment and increases in associated costs, particularly ongoing compliance expenses and resource allocation needs; vendor quality and efficiency; the Company’s ability to control risks associated with rapidly changing technology both from an internal perspective as well as for external providers; operational systems or infrastructure failures; increased competition; fluctuating interest rates; a tightening of available credit; the potential adverse impact of legal or regulatory proceedings; and risks related to the business combination transaction involving Pacific Continental and Columbia, including (i) the possibility that the merger does not close when expected or at all because required regulatory, shareholder or other approvals and other conditions to closing are not received or satisfied on a timely basis or at all; (ii) changes in Columbia’s stock price before closing, including as a result of the financial performance of Pacific Continental prior to closing, or more generally due to broader stock market movements, and the performance of financial companies and peer group companies; (iii) the risk that the benefits from the transaction may not be fully realized or may take longer to realize than expected, including as a result of changes in general economic and market conditions, interest and exchange rates, monetary policy, laws and regulations and their enforcement, and the degree of competition in the geographic and business areas in which Columbia and Pacific Continental operate; (iv) the ability to promptly and effectively integrate the businesses of Columbia and Pacific Continental; (v) the reaction to the transaction of the companies’ customers, employees and counterparties; (vi) diversion of management time on merger-related issues; (vii) lower than expected revenues, credit quality deterioration or a reduction in real estate values or a reduction in net earnings; and (viii) other risks that are described in Columbia’s and Pacific Continental’s public filings with the SEC. Pacific Continental Corporation undertakes no obligation to publicly revise or update any forward-looking statement to reflect the impact of events or circumstances that arise after the date of this release. This statement is included for the express purpose of invoking the PSLRA’s safe harbor provisions.

IMPORTANT INFORMATION FOR INVESTORS AND SHAREHOLDERS

This communication is being made in respect of the proposed merger transaction involving Columbia Banking System and Pacific Continental. This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of such jurisdiction. In connection with the proposed transaction, Columbia has filed with the SEC a Registration Statement on Form S-4 that includes a Joint Proxy Statement of Columbia and Pacific Continental and a Prospectus of Columbia, as well as other relevant documents concerning the proposed transaction. Shareholders of Columbia and Pacific Continental are urged to carefully read the Registration Statement and the Joint Proxy Statement/Prospectus regarding the transaction in their entirety and any other relevant documents filed with the SEC, as well as any amendments or supplements to those documents, because they contain important information. A definitive Joint Proxy Statement/Prospectus will be sent to the shareholders of each institution seeking any required shareholder approvals. The Joint Proxy Statement/Prospectus and other relevant materials filed with the SEC may be obtained free of charge at the SEC’s Website at http://www.sec.gov. Columbia and Pacific Continental shareholders are urged to read the Joint Proxy Statement/Prospectus and the other relevant materials before voting on the transaction. Investors will also be able to obtain these documents, free of charge, from Pacific Continental by accessing Pacific Continental’s website at www.therightbank.com under the link “Investor Relations” or from Columbia at www.columbiabank.com under the tab “About Us” and then under the heading “Investor Relations.” Copies can also be obtained, free of charge, by directing a written request to Columbia Banking System, Inc., Attention: Corporate Secretary, 1301 A Street, Suite 800, Tacoma, Washington 98401-2156 or to Pacific Continental Corporation, Attention: Corporate Secretary, 111 West Seventh Avenue, P.O. Box 10727, Eugene, Oregon 97440-2727.

Pacific Continental and Columbia and their respective directors and executive officers and certain other persons may be deemed to be participants in the solicitation of proxies from the shareholders of Columbia and Pacific Continental in connection with the merger. Information about the directors and executive officers of Columbia and their ownership of Columbia common stock is set forth in the proxy statement for Columbia’s 2017 annual meeting of shareholders, as filed with the SEC on a Schedule 14A on April 13, 2017. Information about the directors and executive officers of Pacific Continental and their ownership of Pacific Continental common stock is set forth in Pacific Continental’s Annual Report of Form 10-K, as amended and filed with the SEC on April 19, 2017. Additional information regarding the interests of those participants and other persons who may be deemed participants in the transaction may be obtained by reading the Joint Proxy Statement/Prospectus regarding the merger when it becomes available. Free copies of this document may be obtained as described in the preceding paragraph.

PACIFIC CONTINENTAL CORPORATION and subsidiary

Consolidated Income Statements

(Dollars in thousands, except share and per share amounts)

(Unaudited)

NA Not applicable

PACIFIC CONTINENTAL CORPORATION and subsidiary

Consolidated Balance Sheets

(Dollars in thousands, except share and per share amounts)

(Unaudited)

NA Not applicable

PACIFIC CONTINENTAL CORPORATION and subsidiary

Loans by Type

(Dollars in thousands)

(Unaudited)

PACIFIC CONTINENTAL CORPORATION and subsidiary

Selected Other Financial Information and Ratios

(Dollars in thousands)

(Unaudited)

PACIFIC CONTINENTAL CORPORATION and subsidiary

Nonperforming Assets, Asset Quality Ratios and Allowance for Loan Losses

(Dollars in thousands)

(Unaudited)