The United Mine Workers of America Local No. 2866 records (1919-1973) contain materials related to the activities of Local No. 2866, located in Roundup, Montana and founded ca. 1910. The materials include correspondence, financial records, subject files on mine safety, Department of Interior notices, organizational records such as memberships, shift schedules, constitutions and bylaws, as well as photographs. The bulk of the materials were created between 1956 to 1962.