In 1893 unions throughout the state sent delegates to the first Washington Labor Congress. In 1902 the Labor Congress decided to form a permanent executive board, change the organization's name to the Washington State Federation of Labor (WSFL), and affiliate with the American Federation of Labor (AFL). Thereafter, only AFL unions could join the WSFL. The primary purpose of the organization, however, remained the same: to lobby the state legislature for labor-endorsed measures. The WSFL also supported candidates and ballot measures and occasionally aided local unions during strikes or organizing drives, but lobbying was almost always the first priority. The WSFL was thus the political arm of the largest segment of the labor movement in Washington.

In the early part of the twentieth century, the WSFL was an important part of the progressive coalition in Washington. The WSFL allied with the Grange, the Federation of Women's Clubs, and other groups to pass a whole host of measures such as workers' compensation, the initiative and referendum, and minimum wage laws for women and children. The WSFL was wracked with internal conflicts in the late 1910s and the 1920s over the US entry into the First World War, the desirability of the industrial union type of organization, and the wisdom of launching a third political party. President William Short (1918-1926) and his moderate craft union allies won most of these disputes. Against the wishes of Short and the AFL hierarchy, the WSFL did, however, vote to help launch the Washington Farmer-Labor Party (FLP) in 1920. The FLP temporarily displaced the Democrats as the primary opposition party in the state but failed to reduce the Republican domination of state politics. In 1922 Short and his allies defeated the third partyists and pulled the WSFL out of the FLP. The WSFL then adopted a non-partisan stance, endorsing both Democratic and Republican candidates. But, other than an increase in workers' compensation benefits in 1923, the Federation won few legislative victories in the conservative 1920s.

The swelling of union membership and the discrediting of conservative leadership during the Great Depression brought the Federation its greatest legislative influence. WSFL President James Taylor (1928-1945) and his staff were instrumental in passing anti-labor injunction bills, legislation creating unemployment insurance, and minimum wage and maximum hour laws in this period. The defection of Congress of Industrial Organizations (CIO) unions, the revival of the Republican Party, and the transfer of many facets of governmental policymaking from the state to the federal level reduced the Federation's power in the late 1930s. Although the WSFL remained influential in state politics, major legislative victories came less often. The Federation won a retirement system for public employees in 1939 and prevailing union wages for all state public works projects in 1945. In addition, President Evan (Ed) Weston (1945-1957) painstakingly crafted numerous incremental expansions of the eligibility criteria and benefit levels of the workers' compensation and unemployment insurance programs during the 1940s and 1950s. In 1957, seeking to expand labor's political power, the Federation set aside its squabbles with rival unions and put itself out of business: the WSFL merged with the Washington State CIO Council to create the Washington State Labor Council.