The Cameron Stewart Collection on the Lincoln Brigade documents American participation in the Spanish Civil War (1936-1939), with particular emphasis on the Abraham Lincoln Brigade. The materials are arranged in three major series: Personal Correspondence and Papers, Publications, and Books and Pamphlets.

The Personal Correspondence and Papers series includes original veteran correspondence, statistical analyses of Brigade membership, and comprehensive documentation of American participants compiled through 1979. The Publications series contains significant runs of contemporary periodicals such as New Masses (1936-1941), Volunteers for Liberty, and various American and international communist publications that covered the conflict. Books and Pamphlets includes Spanish Civil War maps, foreign language materials, and Daily Worker volumes.

The collection also contains Stewart's research manuscripts, student dissertations and papers on the Spanish Civil War, and research materials about nationalist organizations including the Ku Klux Klan (1920-1965). While the majority of materials date from 1936-1939, the collection includes some materials through the early 1940s.

These materials provide valuable documentation of American volunteer participation in the Spanish Civil War and subsequent scholarly research on the topic.