The United Steelworkers union asked union workers at nine U.S. refineries to stop working after a national contract covering dozens of oil facilities expired on Monday. Take a look back at the 10 biggest strikes in U.S. history.
7. 1956 Bituminous Coal Strike -- On April Fools’ day of 1946, the United Mine Workers of America called on 400,000 bituminous coal miners in 26 states to strike for safer conditions, health benefits and pay. The strike lasted until December.