On April 16, 1862, President Abraham Lincoln signed a bill ending slavery in the District of Columbia. Passage of this act came 9 months before President Lincoln issued his Emancipation Proclamation. The act brought to conclusion decades of agitation aimed at ending what antislavery advocates called "the national shame" of slavery in the nation's capital.

April 15 is the deadline for most Americans to file their Federal individual income tax returns. Passed by Congress on July 2, 1909, and ratified February 3, 1913, the 16th amendment established Congress’s right to impose a Federal income tax. In 1913, due to generous exemptions and deductions, less than 1 percent of the population paid income taxes at the rate of only 1 percent of net income.

On April 14, 1865, as he sat in Ford’s Theater watching a comedy, President Lincoln was assassinated. The District of Columbia Metropolitan Police blotter lists the assassination among the more mundane police business of April 14, 1865. The entry begins: "At this hour the melancholy intelligence of the assassination of Mr. Lincoln, President of the U.S, at Fords Theater was brought to this office, and information obtained from the following persons goes to show that the assassin is a man named J. Wilks [sic] Booth…"

Written on April 13, 1989, this letter was sent from second-grader Kelli Middlestead of the Franklin School in Burlingame, California, to Walter Stieglitz the Regional Director of the Alaska Region of the U.S. Fish and Wildlife Service, lamenting the Exxon Valdez oil spill of March 24, 1989.

This prophetic letter was dictated by Truman before President Roosevelt’s death later that same day.

Taken by Dorothea Lange on April 11, 1940, the caption of this photo reads “Edison, Kern County, California. Young migratory mother, originally from Texas…”

“Opening Day of 1961 Baseball Season. President Kennedy throws out the first ball… Washington, D.C., Griffith Stadium, 04/10/1961.”