The following list occurs to me. I am not trying at this point to limit it to 10. Please add, cut, rank. Thanks.
The discovery of the steam engine and/or cotton gin The completion of the transcontinental railroad/Chinese immigration to build it The formation of the great Trusts: Standard Oil, US Steel The Haymarket rally/8 hour day The ARU strike and/or the Homestead strike (a Penna event) Ford's Model T assembly line, Blacks move north to get factory jobs The Triangle Shirtwaist Fire/ILWGU The Lawrence Strike/IWW Something about the CIO--the UMW battles (very important in Penna), maybe the Ford Hunger Strikers? The signing of the NLRA Industry/labor in WWII: women in the industrial workforce, Rosie the Riveter The Treaty of Detroit The civil rights movement and the Civil Rights Act of 1964 Something about the computer industry, what? IBM, Microsoft Something about deindustrialization, moving offshore, maybe US Steel gets out of the steel biz?, becomes USX The breaking of the PATCO strike Something about the service economy, what? ???
--jks