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.
4. Steel Strike of 1919 -- In September 1919, United States Steel Corporation workers in Pittsburgh organized a strike against poor working conditions, long hours, low wages and corporate harassment regarding union involvement. The strike failed and eventually broke up in January 1920, resulting in an absence of union organization in the steel industry for the next 15 years.