April 1, sometime in the 1500s, is the best guess for the start of the April Fool’s Day festivities.
April 3, 1948, President Harry S. Truman signed the European Recovery Program better known as the Marshall Plan. It was intended to stop the spread of Communism and rebuild the economies of Europe devastated by World War II.
April 9, 1866, the Civil Rights Bill of 1866 was passed by Congress granting blacks the rights and privileges of U.S. citizenship despite a veto by President Andrew Johnson.
April 9, 1942, in the Philippines, the Bataan Death March began. American and Filipino prisoners were forced on a six-day, 60 miles march from Bataan to Cabanatuan without food or water.
April 11, 1945, the 6th Armored Division, part of the Third Army liberated The Nazi concentration camp at Buchenwald.
April 14, 1865, President Abraham Lincoln was shot while watching a performance of Our American Cousin at Ford’s Theater in Washington. He died April 15 at 7:22 a.m.
April 18, 1775, The Midnight Ride of Paul Revere and William Dawes occurred as the two men rode out of Boston to warn patriots of the approaching British.
April 19, 1775 – Dawn in Massachusetts, about 70 armed militiamen stood at Lexington Green against a British advance guard unit. An unordered ‘shot heard around the world’ began the American Revolution. https://www.loc.gov/item/today-in-history/april-19/