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.
8. Steel Strike of 1959 -- More than 500,000 steel workers walked off the job nationwide in November 1959 over a demand for higher wages and to protect a contract clause that guaranteed worker jobs and hours. They won their case on both issues.