In 1902, 140,000 coal miners left work in the United Mine Workers strike. Workers were protesting low wages and dangerous working conditions, and were up against wealthy mine owners opposed to change. Coal prices rose drastically, many Americans could no longer heat their homes, and President Theodore Roosevelt saw the threat of riots. Roosevelt intervened, nationalized the mining industry, and commissioned armies to staff them. Roosevelt successfully ended the strike, but was criticized for violating his Constitutional authority in so doing. Roosevelt argued that ending the strike was his moral duty, and worth the breach of presidential duties.