Labor history of the United States - Wikipedia
Strike! Why Mothballing Labor's Key Weapon is Wrong - In These Times
1924 Split of the Industrial Workers of the World - IWW History Project
History of Labor Unions in the US
Bleeding Heartland
Strikes & Unions - Great Depression Project
Labor in Virginia during the Twentieth Century - Encyclopedia Virginia
Labor Wars in the U.S., American Experience, Official Site
Union decline and rising inequality in two charts
Economist's View: 'Was the Decline of American Unions Inevitable?