International Brotherhood of Teamsters Local 85 of San Francisco was founded in August 1900, with an initial membership of thirty-five men. The teamsters organized in response to the appearance of the Draymen's Association, an alliance of San Francisco team-owners, which had been founded in January of that year.

The union was put to an immediate test. On Labor Day, 1900, the large draying firm McNab & Smith fired three teamsters who belonged to the new union. About one hundred of the firm's other drivers promptly went on strike, and the three men were reinstated the next day. This incident convinced more than 1,300 teamsters to apply for membership at the next union meeting.

On October 1, 1900, Teamsters Local 85 entered into an agreement with the Draymen's Association that established a higher, standard daily wage; a twelve-hour work day; and guaranteed overtime pay for work on Sundays, holidays, or after 6 p.m. The contract also included a stipulation that the Draymen's Association would employ only members of the union, and that the union would work only for employers affiliated with the Draymen's Association.

Teamsters Local 85 was led by Michael "Bloody Mike" Casey (1857-1937) and John P. McLaughlin (1873-1949). Born in Ireland, Casey, a charter member of Local 85 and its first business agent, served as the union's president for more than thirty years. In 1904 he was elected one of the International Brotherhood of Teamsters' (IBT) seven regional vice presidents and the chief IBT representative and organizer for the entire United States west of Chicago. McLaughlin, like Casey a charter member of Local 85, acted as its secretary for nearly fifty years. He also served as State Labor Commissioner, administrator of the first Workmen's Compensation Act, Collector of Internal Revenue, and member of the Public Utilities Commission.

In April 1901, the Draymen's Association joined forces with a variety of San Francisco wholesale merchants, manufacturers, and retail merchants in a new employer's union, the Employers' and Manufacturers' Association. The Employers' and Manufacturers' Association collected a $250,000 war chest to combat unionism and managed to put down several small strikes in May and June, 1901. In July, when members of Teamsters 85 were ordered by the Draymen's Association to haul luggage for a nonunion company, Casey led more than 2,500 teamsters on a strike. On July 30 between 10,000 and 16,000 sailors, firemen, and longshoremen who were affiliated with the City Front Federation joined the teamsters in a sympathy strike throughout the Bay Area. The strike ended only after Governor Henry T. Gage stepped in on October 2. The exact terms of the settlement were never revealed, but the strike demonstrated the power and solidarity of San Francisco labor, helped launch the Union Labor Party, triggered the dissolution of the Employers' and Manufacturers' Association, and vindicated the teamsters' right to organize and bargain collectively.

Also in 1901, Teamsters Local 85 joined with Oakland's Local 70 and other Bay Area Teamsters locals in organizing a central organization called the Team Drivers Joint Executive Council. After the 1906 earthquake and fire, the Team Drivers Joint Executive Council was reorganized as San Francisco Bay Area Joint Council 7.

Of the four western Teamsters Joint Councils, San Francisco Bay Area Joint Council was, according to one historian, "by far the largest, most powerful, and unquestionably the most conservative." B the 1920s and 1930s San Francisco's Teamsters Local 85 was "so large, wealthy, well-established, and secure in its position" that it resisted organizing California's plentiful highway truckers, a move Teamsters locals in Seattle and Oakland eagerly embraced in the mid-1930s. Casey finally bowed to IBT pressure in 1935 and helped launch the Bay Area Highway Organizing Drive, later followed by the Highway Drivers Council of California.

During the San Francisco maritime and general strike of July 1934, strike leader Harry Bridges appealed to the members of Teamsters 85 to join his longshoremen in a sympathy strike. On July 11, the Teamsters overwhelming voted in favor of the sympathy strike, considerably strengthening the longshoremen's position.

Mike Casey died in 1937, and John P. McLaughlin took over as IBT vice president. That same year, Local 85 joined approximately 150 other Teamster locals in eleven western states to form the Western Conference of Teamsters, led by Seattle Teamster Dave Beck. The creation of this multi-jurisdictional regional body, unprecedented in Teamster history, significantly shifted the balance of Teamster power westward. Beck himself rose to become president of the IBT in 1952.