20 August 1619 – The 1st African slaves arrived in North America aboard a Dutch privateer. It docked in Jamestown, Virginia, with twenty human captives among its cargo. 1775 – The Spanish establish the Presidio San Augustin del Tucson in the town that became Tucson, Arizona. 1804 – Sergeant Charles Floyd dies three months into the voyage of Meriwether Lewis and William Clark, becoming the only member of the Corps of Discovery to die during the journey. 1861 - PSS R. W. Powell was a Confederate side-wheel steamer of 349 tons, built in 1855 at New Albany, Ind. that snagged at Plaquemine, Louisiana. 1861 - T. W. Riley was a Union sloop that was scuttled near the sloop Jane Wright by the USS Yankee and USS Restless at Wades Bay, Potomac River, to prevent its use by Confederates. 1863 - SS William S. Bull was a Union steamer of 16 tons built in 1861 at Buffalo, Ny. She foundered this date about 40 miles from Erie, PA. 1864 - SV Roan was a Union Brig of 127 tons that was captured and burnt by the CSS TALLAHASSEE south of Halifax, Nova Scotia while in ballast to Cape Breton Island. 1908 – The American Great White Fleet arrived in Sydney, Australia, to a warm welcome. 1910 – The 1st shot fired from an airplane was during a test flight over Brooklyn’s Sheepshead Bay. 1936 - Prototype Vought XSB2U-1 Vindicator, BuNo 9725, first flown at Rentschler Field, East Hartford, Connecticut, on 5 January 1936, accepted by the U.S. Navy on 2 July 1936, crashes near Norfolk, Virginia. During stall tests at low altitude (1,000 feet), the aircraft spun into shallow water of Willoughby Bay, killing the two aboard, pilot Lt. Cmdr. Samuel Hyer Arthur, and Chance Vought observer Robert Witbeck. Testing had sufficiently advanced, however, that a contract was signed on 26 October 1936 for 54 aircraft. The aircraft made its first flight on 21 May 1937 and deliveries to operational units began in December 1937. 1940 – Radar was used for the first time, by the British during the Battle of Britain. 1941 – Adolf Hitler authorized the development of the V-2 missile. 1942 – Plutonium was first weighed. Glenn T. Seaborg was a co-discoverer of Plutonium. 1945 – The War Production Board removes most of its controls over manufacturing activity. These and many other measures help the US economy to convert quickly to a peacetime basis. The American economy is actually stronger and more productive now, than before the war, and the standard of living, unlike that of any of the other major participants in the war, has actually increased. 1946 – World War II civilian truck restrictions were lifted in the U.S. Truck restrictions were only the beginning of special regulations during the war. 1946 - A captured Messerschmitt Me 262A, Wrknr. 111711, FE-0107, 711, crashed Tuesday afternoon ~two miles S of Xenia, Ohio, near Route 68, test pilot Walter J. McAuley, Jr., of the Flight Performance Section, Flight Test Division, Wright Field, Ohio, successfully parachuting to safety. This brand new airframe had been surrendered on 31 March 1945 by Messerschmitt test pilot Hans Fay who defected during a functional check flight rather than fly it to an operational unit, landing at Rhein-Main, Frankfurt, the first Me 262 to fall into Allied hands. 1948 - A Boeing B-29-15-BA Superfortress, 42-63442, crashes near Rapid City, South Dakota shortly after take-off from Rapid City AFB, killing all 17 on board. 1953 – The Soviet Union publicly acknowledged it had tested a hydrogen bomb. 1962 – Test pilot Robert Rushworth flew the X-15 to 27,097 meters (88,900 feet) and Mach 5.24. 1968 – In the face of rising anti-Soviet protests in Czechoslovakia, Soviet troops (backed by troops from other Warsaw Pact nations) intervene to crush the protest. 1974 – In the wake of Nixon’s resignation, Congress reduces military aid to South Vietnam from $1 billion to $700 million. This was one of several actions that signaled the North Vietnamese that the United States was backing away from its commitment to South Vietnam. 1975 – Viking 1, an unmanned U.S. planetary probe, is launched from Cape Canaveral, Florida, to soft-land on Mars. 1977 – The United States launched Voyager 2, an unmanned spacecraft to explore the outer solar system. 1998 – Pres. Clinton ordered cruise missile attacks on Sudan and Afghanistan 13 days after the deadly embassy bombings in East Africa. About 50 missiles were fired at the camp of Osama Bin Laden and some 25 missiles against a suspected chemical plant in Khartoum.