April 4, 1818: Congress decides on the US flag: 13 red & white stripes & 20 stars.
April 5, 456: Saint Patrick returns to Ireland as a missionary bishop.
April 6, 1862: Battle of Shiloh, Union defeats Confederacy near Pittsburg Landing, Tennessee.
April 7, 1944: World War II: General Montgomery speaks to generals at St. Paul's School about his vision for the upcoming D-Day landings.
April 8, 1796: Carl Friedrich Gauss, German mathematician, proves the quadratic reciprocity law (the ability to determine the solvability of any quadratic equation in modular arithmetic).
April 9, 1768: John Hancock refuses to allow two British customs agents to go below deck of his ship, considered by some to be the first act of physical resistance to British authority in the colonies.
April 10, 1869: Congress increases number of Supreme Court judges from 7 to 9.