Before the Emancipation Proclamation and before the 13th Amendment to the Constitution, which outlawed slavery, there was the District of Columbia Compensated Emancipation Act.

Next month marks the sesquicentennial of the pioneering federal law that in 1862 freed 3,100 slaves in Washington, and Wednesday city officials announced a series of events to celebrate the 150th anniversary.

They include, among other things, an Emancipation Parade on April 16 along Pennsylvania Avenue NW, a street festival the same day at Freedom Plaza, and a march among the Mall memorials April 11.

There will also be a lectures, concerts, films and ceremonies related to slavery, emancipation and civil rights at the African American Civil War Museum, the Abraham Lincoln cottage, the Frederick Douglass home and other venues across the city in April.

The compensated emancipation act was signed into law by President Lincoln on April 16, 1862 — nine months before he issued the broader and more famous Emancipation Proclamation in 1863.

The District act freed slaves, provided for up to $300 per slave in compensation to the owners, and offered up to $100 to each freed slave who moved to another country.

The District’s emancipation day was, for many years in the late 1800s, the occasion of parades and festivities, Mayor Vincent C. Gray said during the announcement at the African American Civil War Museum, on Vermont Avenue NW.

Its popularity has ebbed and flowed since then, but it became a city holiday in 2005.