Cadomin's name is an acronym for 'Canadian Dominion Mining'. Cadomin is one of many communities in the Alberta Coal Branch area that thrived from the 1920s to the 1950s. During the early 1930s, Cadomin's population peaked at 1,800. Other Coal Branch communities included Mountain Park, Luscar, Mercoal, and farther to the east, Robb, Embarras, Coalspur, Coal Valley, Lovett, and Foothills.
The Post Office opened on August 15, 1918.