August 21
Slave revolt led by Nat Turner begins in Southampton County, Va. - 1831
And this:

August 21, 1831 - Nat Turner launched a slave revolt in Southhampton County, Virginia. The two-day insurrection led by Turner and 75 followers left 60 whites dead. In the rebellion's aftermath, scores of African-Americans were lynched, though many were non-participants in the revolt.
For more on Nat Turner and the slave trade, go to
http://www.pbs.org/wgbh/aia/part3/3p1518.html and
http://memory.loc.gov/ammem/aaohtml/aopart1.htmlLabor history found here:
http://www.unionist.com/big-labor/today-in-labor-history & here:
http://www.workdayminnesota.org/index.php?history_9_08_21_2011