The California CIO was built in the mid-1930s during a period of increased union activity and organizing. The Labor Herald, published weekly, recorded CIO activity from 1937 to 1953. The paper began as a voice for the CIO in Northern California; in 1941, it extended its coverage to all of California. A Southern California edition and a Southern California editor was added in 1945. Unions made per capita payments to support the newspaper and this provided a subscription to each member. The California CIO came under progressive, left-wing leadership under such officers as Harry Bridges and Philip Connelly. The photo collection records its activities, especially during the 1940s, the World War II years and the post-war period which saw strikes and a major political battle against the Taft-Hartley Bill.

The California CIO and its support to the Labor Herald was severely cut back in 1949 when the CIO leveled charges of communist-dominated leadership against eleven national unions as well as the California CIO. In November 1949, these unions were expelled from the CIO. Their charters were lifted along with that of the California CIO. The Labor Herald continued publication with some support coming from those unions which survived the subsequent raids by AFL or newly chartered CIO unions. After 1952, Harold Rossman, the paper's editor since 1941, departed and his position was filled on a voluntary basis by Paul Chown until the Labor Herald ceased publication in May 1953.