The boilermakers in San Francisco have a long history of organization. By 1867, a group identified as the Journeymen Boilermakers' Protective Union became a part of the San Francisco Trades' Union. They were among the founding unions of the Federated Iron Trade Council of San Francisco in 1885. The International Brotherhood of Boilermakers, Iron Ship Builders and Helpers was organized in 1893, and the San Francisco lodge received its charter in 1900.

The work of boilermakers is heavy-gauge metal fabrication and includes welders, burners, drillers, and rollers. Among the many industries employing boilermakers are manufacturing, railroad, dams, and shipbuilding. Lodge 6's records include the World War II period when tremendous growth and changes occurred in these industries. There was a boom in shipbuilding on the Pacific Coast and the boilermakers were among the trades negotiating master contracts for shipbuilding and manufacturing as members of the Pacific Coast Metal Trades Council and the Bay Area Metal Trades Council. The years of World Was II also saw African-Americans and women struggling to becoming members of Lodge 6 for the first time.

This collection documents the unique career of a labor leader named Edgar Rainbow, a Native American (Cherokee). Mr. Rainbow was first elected business manager of Lodge 6 in 1936 and continuously held that position for 36 years until 1972. He also served concurrently as president of the Lodge from time to time and was a prominent figure in the Bay Area Metal Trades Council.

Ira B. Cross, A History of the Labor Movement in California (Berkeley: University of California Press, 1935), pp. 32-36.