Local No. 2866 was established ca. 1910 in Roundup, Montana as a local branch of the United Mine Workers of America Union. United Mine Workers of America was formed in 1890 in an effort to combat unfair wages, unsafe working conditions, and to help establish an eight-hour workday. By 1919, Local No. 2866 had 315 members, 44 of whom served in the army during World War 1, although membership declined by the 1940s and 1950s. The coal mines in Roundup underwent an extensive series of inspections from 1957 to 1970. In 1957, following an inspection by Federal Mining Inspectors E. L. Christensen and Andrew Kipp, mines No. 2 and No. 3, located in Klein and Roundup respectfully, were shut down due to questionable circumstances and safety violations. On January 18, 1957, having completed repairs, the mines reopened. In May of 1962, E. L. Christensen conducted another spot check of Roundup Mine No. 3’s emergency escapeway and found several safety violations. Christensen submitted Form A. Notice to withdraw employees from that area of the mine until it had been repaired. Little to no repairs took place over the following month, leading the Local No. 2866’s safety committee team, including members William J. Glancy and Stanley Blazina, to report the unsafe conditions to the Safety Director of United Mine Workers in Washington D.C, resulting in another inspection from E.L Christensen in June 1962. Further mining inspections of mines in the Roundup region took place in 1970, resulting in several more safety violations and notices from the Department of the Interior.