Emancipation Day celebrates the end of slavery in Washington, DC

An engraving of DC's black community celebrating when slavery was ended in the District of Columbia in 1862.

If you haven't touched your taxes yet this year, here's some good news: A holiday celebrated only in Washington, DC, has bought you a few extra days. For most Americans, federal taxes are due Monday, April 18, rather than Friday, April 15.

That's because tax filing deadlines are pushed back to the next business day if April 15 falls on a weekend, a federal holiday, or a holiday celebrated in Washington, DC.

And this year April 15 is a holiday in the District of Columbia. Emancipation Day, usually celebrated on April 16, falls on a Saturday, so it's being observed on Friday, April 15 — Tax Day — instead. (Maine and Massachusetts residents have until April 19 to file their taxes: April 18 is Patriot's Day, which commemorates the battles of Lexington and Concord during the Revolutionary War.)

But if you only know about Emancipation Day because it gave you a break on rushing to finish your taxes, you're missing that the holiday itself has a fascinating history.

In 1862, eight months before the Emancipation Proclamation, Congress passed a law ending slavery in Washington, DC — a long-held goal of abolitionists, including President Abraham Lincoln, who had been fighting to end slavery in the nation's capital since 1849.

Lincoln signed the law on April 16, 1862. At the time, about 3,300 slaves were living in the District, outnumbered two to one by free black residents. To free them, Congress paid slaveholders an average of $300 per slave. And to get their money, slave owners had to file petitions with details about the slaves that were going to be freed. Read More here