Up until the post Civil War era, most of this valley was farm land and small surface or near-surface mining areas.
In 1891 American labor peace was broken with the uprising of steel workers in Homestead, Pennsylvania.
For days the city and its massive steel mill were taken over by the workers, repelling attacks by a small army of Henry Clay Frick (U.S. Steel) hired Pinkertons and local law enforcement until finally the issue was resolved by what would become the Pennsylvania National Guard.
During World War I and II the valley was affectionately known as the "Arsenal of Democracy" for being the leading single source of American armaments and weaponry.
Joe Namath, Tony Dorsett, Dan Marino, Joe Montana, Johnny Unitas, Curtis Martin, Ty Law, Kevan Barlow, Jim Kelly, and Mike Ditka all grew up in the actual geographic valley.