April 4.
1660. Charles II issues the Declaration of Breda, setting forth the conditions for his acceptance of the crown, and cementing the terms for the ending of the Commonwealth period.
1818. The United States Congress sets forth the formal design for the United States flag, with 13 red and white stripes and a star for each state. Previously, the flag had included a strip for each state, leading to some odd looking (to our modern eyes) flags.
15 stripe flag in use from 1795 to 1818:
1841. President William Henry Harrison dies, becoming the first President to die in office and the one with the shortest term. "Tippecanoe", wanting to show he was still the tough, steadfast military hero, gave the longest inaugural speech in American history on a cold, rainy day (March 4, the old day on which Presidents were inaugurated) without either a topcoat or hat. After the two hour speech, he rode through the city in the inaugural parade. A month later, he died of pneumonia. Harrison died nearly penniless, and Congress voted his widow a pension of $25,000, equivalent to $500,000 in 2009 dollars, and the right to mail letters for free.
1850. Los Angeles, California, is incorporated as a city.
1865. President Lincoln arrives in the city of Richmond, Virginia, captured only one day earlier by Union forces. He is accompanied by his son, Tad, and it is Tad's 12th birthday.
1975. Bill Gates and Paul Allen team up and form the Microsoft corporation.