Worst Mining Disaster in U.S. History

    
     On December 6, 1907, methane gas (fire damp) exploded in mine tunnels 6 and 8 of the Fairmont Coal Company in Monongah, West Virginia. More than 362 miners including child laborers--breaker boys or slate pickers--were killed. Rescue workers also died by suffocation in oxygen-depleted tunnels filled with black damp*. Current research by the U.S. Department of Labor suggests that the number of deaths was nearer 500. The exact number remains unknown.
     The majority of miners killed were Italian-American immigrants. One hundred seventy one died. Many of the dead were fathers with large families. The mining disaster is remembered in Italy to this day. A movie called Monongah, La Marcinelle Americana by Silvano Console commemorates the tragic loss of life. A flash video in English is also available at West Virginia PBS--Monongah Mine Disaster.
      By the end of 1907,  3,242 workers had died in mining accidents across the United States, leading to renewed efforts for mine safety and greater influence by the United Mine Workers. 
     In 1913, the second worst mining disaster in the United States occurred at a coal mine in Dawson, New Mexico. Two hundred sixty three miners were killed.
     In 1909, the third worst mining disaster in the United States occurred in Cherry, Illinois.Two hundred fifty nine coal miners were killed. Unconfirmed counts put the number at more than four hundred killed.

Reference:
1) Wikipedia--Monongah Mining Disaster
 
2) Monongah Bell Donated by Italy--Pittsburg Post-Gazette

3) Rootsweb

* Black damp is a mixture of carbon dioxide and nitrogen.