The District has been celebrating Emancipation Day since the 19th century to commemorate President Abraham Lincoln's emancipation of slaves in the District of Columbia more than nine months before the Emancipation Proclamation freed slaves throughout the U.S.
It wasn't until 2005, however, that the day -- April 16 -- was named an official public holiday. Because it falls on a Saturday this year, the District is observing the day Friday, April 15.
Because District holidays are treated as federal holidays for the purposes of tax deadlines, D.C.'s celebration becomes a boon for residents all over the U.S.; rather than the usual April 15, the federal IRS tax deadline is April 18 this year.
The District government closure also means a parking free-for-all, an extra day off for D.C. Public Schools students and a free day for District employees. DCist has an overview of what's closed and open today.