Seafirst Corporation was a bank holding company based in Seattle, Washington. Formed on November 11, 1929, from the merger of Seattle's three largest banks, the First National Bank Group, the Dexter Horton National Bank (founded 1870 by Dexter Horton), and Seattle National Bank, the bank was originally named First Seattle Dexter Horton National Bank. In 1931, the bank changed its name to First National Bank of Seattle, and again in 1935 to Seattle-First National Bank. In 1944, the bank won a case before the US Supreme Court, United States v. Seattle-First Nat. Bank, by arguing that it did not have to pay a transfer tax when it converted from a state to a federally chartered bank. In 1970 it was using the name Firstbank; in 1974 the name Seafirst was adopted instead.
Seafirst was acquired by BankAmerica Corp. in 1983, when Seafirst was at risk of seizure by the federal government after becoming insolvent following the demise of Oklahoma City-based Penn Square Bank. Seafirst had acquired a significant share of Penn Square's energy loan debt by participating in loans originated by that bank. Penn Square Bank collapsed in 1982, and the FDIC's decision to pay off only insured deposits rendered the participation assets valueless. The corporation and its primary subsidiary, Seattle-First National Bank, maintained the Seafirst Bank name and brand identity. During the 1980s and much of the 1990s Seafirst Bank maintained a high degree of autonomy and reigned as the largest bank in Washington.