April 16 (UPI) -- On this date in history:
In 1862, the U.S. Congress abolished slavery in the District of Columbia.
In 1912, as crowds gathered outside its New York City offices, the White Star Line denied that it was withholding information on the sinking of RMS Titanic.
In 1947, a fire aboard the French freighter Grandcamp in the Texas City, Texas, port on Galveston Bay ignited ammonium nitrate and other explosive materials in the ship's hold, causing a massive blast that destroyed much of the city and killed nearly 600 people.
In 1972, Apollo 16 blasted off on an 11-day moon mission with three astronauts aboard.
In 1990, Dr. Jack Kevorkian helped in his first assisted suicide. In December, he was charged with murder for the death of a woman with Alzheimer's disease, who died using his so-called suicide machine in June.
In 1991, the first Jewish settlement under the Israeli government opened in the occupied territories, defying a U.S. request to stop settlement activity in the West Bank and Gaza Strip.
In 1999, hockey legend Wayne Gretzky announced his retirement from the NHL after 21 years. He was inducted into the NHL Hall of Fame in November without having to go through the usual three-year waiting period.
In 2002, Dutch Prime Minister Wim Kok and members of his government resigned after a report faulted them, along with the United Nations, for failing to prevent the 1995 massacre of 7,500 Muslim men and boys at Srebrenica, Bosnia.
In 2007, Seung-Hui Cho, a senior at Virginia Tech, went on a campus shooting rampage, killing 32 people before killing himself.
In 2011, a vicious rash of tornadoes tore through 14 U.S. states, leaving more than 40 people dead and many others homeless.