April 2, 1513 - Spanish explorer Ponce De Leon sighted Florida and claimed it for the Spanish Crown after landing at the site of present day St. Augustine, now the oldest city in the continental U.S.
April 1, 1998 - A federal judge in Little Rock, Arkansas, dismissed a sexual harassment case against President Bill Clinton, stating the case has no "genuine issues" worthy of trial. A former Arkansas state employee had claimed that in 1991 then-Governor Clinton asked her for sex in a Little Rock hotel room and charged that Clinton's actions amounted to sexual harassment. President Clinton denied any wrongdoing. A unanimous ruling by the U.S. Supreme in May of 1997 allowed the case to precede against President Clinton, thus establishing a precedent allowing sitting presidents to be sued for personal conduct that occurred before taking office. In 1982, the Court had ruled that a president cannot be sued for civil damages for carrying out official duties - as a result of a suit brought against President Richard Nixon by a fired Air Force manager.
April 3, 1995 - Supreme Court Justice Sandra Day O'Connor became the first woman to preside over the Court, sitting in for Chief Justice William H. Rehnquist who was out of town.
April 4, 1949 - Twelve nations signed the treaty creating NATO, the North Atlantic Treaty Organization. The nations united for common military defense against the threat of Soviet expansion in Western Europe.
April 6, 1917 - Following a vote by Congress approving a declaration of war, the U.S. entered World War I in Europe
April 9, 1865 - After 500,000 American deaths, the U.S. Civil War effectively ended as Gen. Robert E. Lee surrendered to Gen. Ulysses S. Grant in the village of Appomattox Court House. The surrender occurred in the home of Wilmer McLean. Terms of surrender, written by Gen. Grant, allowed Confederates to keep their horses and return home. Officers were allowed to keep their swords and side arms.
April 10, 1942 - During World War II in the Pacific, the Bataan Death March began as American and Filipino prisoners were forced on a six day march from an airfield on Bataan to a camp near Cabanatuan. 76,000 Allied POWs including 12,000 Americans were forced to walk 60 miles under a blazing sun without food or water to the POW camp, resulting in over 5,000 American deaths.
April 12, 1861 - The U.S. Civil War began as Confederate troops under the command of Gen. Pierre Beauregard opened fire at 4:30 a.m. on Fort Sumter in Charleston, South Carolina.
April 15, 1912 - In the icy waters off Newfoundland, the luxury liner Titanic with 2,224 persons on board sank at 2:27 a.m. after striking an iceberg just before midnight. Over 1,500 persons drowned while 700 were rescued by the liner Carpathia which arrived about two hours after Titanic went down.
April 18, 1775 - The Midnight Ride of Paul Revere and William Dawes occurred as the two men rode out of Boston about 10 p.m. to warn patriots at Lexington and Concord of the approaching British.
April 18, 1906 - The San Francisco Earthquake struck at 5:13 a.m. followed by a massive fire from overturned wood stoves and broken gas pipes. The fire blazed for three days resulting in the destruction of over 10,000 acres of property and 4,000 lives lost.
April 21, 1836 - The Battle of San Jacinto between Texans led by Sam Houston and Mexican forces led by Santa Anna took place near present day Houston. The Texans decisively defeated the Mexican forces thus achieving independence.
April 22, 1864 - "In God We Trust" was included on all newly minted U.S. coins by an Act of Congress.
April 30, 1789 - George Washington became the first U.S. President as he was administered the oath of office on the balcony of Federal Hall at the corner of Wall and Broad Streets in New York.