Thanks to a quirk in this year's income tax filing deadline, many Americans are getting a lesson in Civil War history today. The IRS pushed back the filing deadline because April 15 landed on Sunday and today is Emancipation Day, which marks the anniversary of the 1862 District of Columbia Emancipation Act.

The act is not well-known, but you could consider it the predecessor of the broader proclamation that President Abraham Lincoln used to free the slaves in Confederate states. According to the National Archives, it "provided for immediate emancipation, compensation to former owners who were loyal to the Union of up to $300 for each freed slave, voluntary colonization of former slaves to locations outside the United States, and payments of up to $100 for each person choosing emigration." It led to the freedom of 2,989 slaves.

The opening paragraph makes for some stirring reading:

Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That all persons held to service or labor within the District of Columbia by reason of African descent are hereby discharged and freed of and from all claim to such service or labor; and from and after the passage of this act neither slavery nor involuntary servitude, except for crime, whereof the party shall be duly convicted, shall hereafter exist in said District.

The broader Emancipation Proclamation -- declaring "that all persons held as slaves [in Confederate states] are, and henceforward shall be free" -- was issued January 1, 1863. It also had its limitations. As the Archives notes, it did not reach border states, where the issue of the expansion of slavery helped touch off the Civil War. It also exempted parts of the Confederacy controlled by the Union.