March 15
March 15, 1869 - The first amendment to grant women’s suffrage was introduced in the U.S. Congress. It would take 50 more years before women would achieve the right to vote.
Official formation of the Painters International Union - 1887
And this:

March 15, 1887 - The Painters International Union was formed. Today, the International Union of Painters and Allied Trades represents more than 140,000 members in the construction industry, such as Painters, Drywall Finishers, Glaziers, Floor Coverers, and Sign and Display workers. Find out more at www.iupat.org
Supreme Court approves 8-Hour Act under threat of a national railway strike - 1917
Bituminous coal miners begin nationwide strike, demanding adoption of a pension plan - 1948
The Wall Street Journal begins a series alleging insider stock deals at the union-owned Union Labor Life Insurance Co. (ULLICO). After three years a settlement was reached with Robert Georgine, a building trades leader serving as ULLICO president and CEO, requiring him to repay about $2.6 million in profits from the sale of ULLICO stock, forfeit $10 million in compensation and make other payments worth about $4.4 million. All but 2 of the company’s directors were said to have profited from the deals - 2002
Labor history found here:
http://www.unionist.com/today-in-labor-history & here:
http://www.workdayminnesota.org/index.php?history_9_03_15_2011