0527 - Justinianus becomes compassionate emperor of Byzantium
1504 - English guilds/corp goes under state control
1578 - William Harvey of England discovers blood circulation
1621 - First treaty between a Native American tribe and a group of American colonists. [H]
1724 - Jonathan Swift publishes Drapier's letters
1748 - Ruins of Pompeii found
1760 - "The Poor Robin's Almanack" published one of the first celebrations of April Fools' Day
1776 - Friedrich von Klinger's "Sturm und Drang," premieres in Leipzig
1778 - Oliver Pollock, a New Orleans businessman, creates "$" symbol
1789 - Enough congressmen arrived in New York City so the U.S. House of Representatives could achieve a quorumand hold its first full meeting. Frederick Muhlenberg of Pennsylvania was elected the first House Speaker.
1792 - Gronings feminist Etta Palm demands women's right to divorce
1826 - Samuel Mory patents internal combustion engine. It was pretty much the kind of engine we use in cars and trucks today.
1862 - Shenandoah Valley campaign, Jackson's Battle of Woodstock, VA
1863 - 1st wartime conscription law in US goes into effect
1865 - -9] Battle at Blakely Alabama
1865 - Battle of 5 Forks Virginia, signalling end of Lee's army
1866 - US Congress rejects presidential veto gives all equal rights in US
1867 - Blacks vote in municipal election in Tuscumbia, Alabama
1867 - Singapore, Penang & Malakka become British crown colonies
1881 - Anti-Jewish riots in Jerusalem
1889 - 1st dishwashing machine marketed (Chicago)
1891 - London-Paris telephone connection opens
1891 - Painter Gauguin leaves Marseille for Tahiti
1918 - The Royal Air Force (RAF) is formed with the amalgamation of the Royal Flying Corps (RFC) and the Royal Naval Air Service (RNAS). [H]
1924 - Hitler sentenced to 5 years labor but Gen Ludendorff acquitted for leading the botched Nazi's "Beer Hall Putsch" in the German state of Bavaria
1927 - 1st automatic record changer introduced by His Master's Voice
1928 - Chiang Kai-shek's army crosses Yang-tse
1929 - Louie Marx introduces Yo-Yo
1930 - "Blue Angel," starring unknown Marlene Dietrich, premieres in America
1930 - Stunt where Leo Hartnett of the Chicago Cubs broke the altitude record for a catch by catching a baseball dropped from the Goodyear blimp 800 feet over Los Angeles, CA. He caught the ball cleanly, saying, Eeeeoooww!". His injuries included a broken jaw.
1933 - Heinrich Himmler becomes Police Commander of Germany (Reichsfuhrer-SS)
1933 - Nazi Germany begins persecution of Jews by boycotting Jewish businesses
1934 - Bonnie & Clyde kill 2 police officers
1935 - 1st radio tube made of metal announced, Schenectady, NY
1939 - US recognizes Franco government in Spain at end of Spanish civil war Pope Pius XII congratulates and blesses Generalissimo Franco's victory in Spain
1941 - Lillian Hellman's "Watch on the Rhine," premieres in NYC
1941 - Navy takes over Treasure Island (SF Bay)
1941 - Nazi's forbid Jews access to cafes in Paris
1942 - Allied air raid on harbor city Kupang Timor
1944 - Japanese troops conquer Jessami, East-India
1945 - Canadian troop free Doetinchem, Enschede, Borculo & Eibergen
1945 - US forces invade Okinawa during WW II, to begin what would be one of the longest and bloodiest battles of World War II. Okinawa is located midway between Japan and Formosa, Okinawa was large enough to provide a base for an invasion of Japan itself. Over 100,000 Japanese defenders were on the island, most troops were deeply entrenched in the densely forested interior. 
1946 - Weight Watchers forms
1946 - Tidal waves struck the Hawaiian islands, resulting in more than 170 deaths.
1947 - 1st Jewish immigrants to Israel disembark at Port of Eilat
1952 - Big Bang theory proposed in Physical Review by Alpher, Bethe & Gamow
1954 - US Air Force Academy forms
1955 - EOKA-bomb attacks against British government buildings in Cyprus
1956 - 10th Tony Awards: Diary of Anne Frank & Damn Yankees win
1960 - TIROS I (Television & Infra-Red Observation Satellite) launched to improve weather prediction.
1960 - U Nu elected premier of Burma
1961 - Jim Bakker marries Tammy Faye
1963 - NYC's newspapers resume publishing after a 114 day strike
1965 - King Hussein bin Talal of Jordanian appointed his younger brother, Prince Hassan bin Talal, as crown prince and heir to the Hashemite throne. This required a change to the Jordan constitution to allow for fraternal succession,
1967 - 1st British ombudsman sir Edward Compton begins work
1970 - President Nixon signed a measure banning cigarette advertising on radio and television, to take effect after Jan. 1, 1971.
1974 - Ayatollah Khomeini calls for an Islamic Republic in Iran
1976 - Stephen Wozniak & Steven Jobs founded Apple Computer
1977 - The U.S. Senate followed the example of the House by adopting a stringent code of ethics requiring full financial disclosure and limits on outside income.
1979 - Iran proclaimed an Islamic Republic following fall of Shah
1982 - The United States formally transferred control of the Panama Canal Zone to the government of Panama.
1983 - Anti-nuke demonstrators link arms in 14-mile human chain in England
1986 - World oil prices dip below $10 a barrel
1987 - In his first major speech on the AIDS epidemic, President Reagan told doctors in Philadelphia, "We've declared AIDS public health enemy No. 1."
1990 - CBS fires sportscaster Brent Mussburger
1990 - It becomes illegal in Salem Oregon to be within 2' of nude dancers
1990 - Jack Nicklaus wins 1st start on Senior PGA tour
1991 - Iran releases British hostage Roger Cooper after 5 years
1991 - Moscow food stores closed to curb panic buying in anticipation of government price increases.
1992 - Battleship USS Missouri (on which, Japan surrendered) decommissioned
1992 - President Bush pledged the United States would help finance a $24 billion international aid fund for the former Soviet Union. 
1992 - The House ethics committee publicly identified 22 current and former lawmakers as the worst offenders in the House bank overdraft controversy.
1993 - Alan Bennett's "Madness of George III," premieres in London
1993 - The FCC ordered the nation's cable television industry to cut its basic monthly rates by about 10 percent.
1994 - Bob Feller Statue on Indians Plaza, dedicated
1996 - An outbreak of "mad cow" disease forced Britain to plan the mass-slaughter of cows.
1997 - Federal authorities cautioned that thousands of schoolchildren across the nation might have been exposed to the hepatitis A virus by eating frozen strawberries imported from Mexico and processed in the United States.
1997 -In the first of two reports, the Justice Department concluded the FBI had erred seriously in its investigation into the July 1996 bombing at Olympic Park in Atlanta.
1998 - Judge dismisses Paula Jones' sexual harassment lawsuit against President Bill Clinton. Some thought it was an April fool's joke.
2000 - The mediator in the Microsoft antitrust case said the software giant and the government had abandoned talks to settle the case.
2001 - A U.S. Navy surveillance plane collided with a Chinese fighter over the South China Sea,  The Chinese plane crashed into the ocean; the damaged U.S. plane landed on the Chinese island of Hainan, where its 24 crewmembers were held for 11 days.
2001 - Former Yugoslav President Slobodan Milosevic was arrested on corruption charges after a 26-hour armed standoff with the police at his Belgrade villa. 
2001 - Notre Dame won its first national championship in women's basketball, defeating Purdue, 66-64.