1478 – Pazzi conspirators attacked Lorenzo and killed Giuliano de’Medici.

1514 – Copernicus made his first observations of Saturn.

1607 – The British established an American colony at Cape Henry, Virginia. It was the first permanent English establishment in the Western Hemisphere.

1819 – The first Odd Fellows lodge in the U.S. was established in Baltimore, MD.

1865 – Joseph E. Johnston surrendered the Army of Tennessee to Sherman during the American Civil War.

1865 – John Wilkes Booth was killed by the U.S. Federal Cavalry.

1906 – In Hawaii, motion pictures were shown for the first time.

1921 – Weather broadcasts were heard for the first time on radio in St. Louis, MO.

1929 – First non-stop flight from England to India was completed.

1931 – New York Yankee Lou Gehrig hit a home run but was called out for passing a runner.

1931 – NBC premiered “Lum and Abner.” It was on the air for 24 years.

1937 – German planes attacked Guernica, Spain, during the Spanish Civil War for the Spanish nationalist government. This raid is considered one of the first to be attacks on a civilian population by a modern air force.

1937 – “LIFE” magazine was printed without the word “LIFE” on the cover.

1937 – “Lorenzo Jones” premiered on NBC radio.

1941 – An organ was played at a baseball stadium for the first time in Chicago, IL.

1945 – Marshal Henri Philippe Petain, the head of France’s Vichy government during World War II, was arrested.

1952 – Patty Berg set a new record for major women’s golf competition when she shot a 64 over 18 holes in a tournament in Richmond, CA.

1954 – Grace Kelly was on the cover of “LIFE” magazine.

1964 – The African nations of Tanganyika and Zanzibar merged to form Tanzania.

1964 – The Boston Celtics won their sixth consecutive NBA title. They won two more before the streak came to an end.

1968 – Students seized the administration building at Ohio State University.

1982 – The British announced that Argentina had surrendered on South Georgia.

1983 – Dow Jones Industrial Average broke 1,200 for first time.

1985 – In Argentina, a fire at a mental hospital killed 79 people and injured 247.

1986 – The world’s worst nuclear disaster to date occurred at Chernobyl, in Kiev. Thirty-one people died in the incident and thousands more were exposed to radioactive material.

1998 – Auxiliary Bishop Juan Gerardi Conedera was bludgeoned to death two days after a report he’d compiled on atrocities during Guatemala’s 36-year civil war was made public.

2000 – Charles Wang and Sanjay Kumar purchased the NHL‘s New York Islanders.

2002 – In Erfurt, Germany, an expelled student killed 17 people at his former school. The student then killed himself.

On April 25, 1945, President Harry S. Truman learns the full details of the Manhattan Project, in which scientists are attempting to create the first atomic bomb. The information thrust upon Truman a momentous decision: whether or not to use the world’s first weapon of mass destruction.

America’s secret development of the atomic bomb began in 1939 with then-President Franklin Roosevelt’s support. The project was so secret that FDR did not even inform his fourth-term vice president, Truman, that it existed. (In fact, when Truman’s 1943 senatorial investigations into war-production expenditures led him to ask questions about a suspicious plant in Minneapolis, which was secretly connected with the Manhattan Project, Truman received a stern phone call from FDR’s secretary of war, Harry Stimson, warning him not to inquire further.)

When President Roosevelt died on April 12, 1945, Truman was immediately sworn in and, soon after, was informed by Stimson of a new and terrible weapon being developed by physicists in New Mexico. In his diary that night, Truman noted that he had been informed that the U.S. was perfecting an explosive great enough to destroy the whole world.

On April 25, Stimson and the army general in charge of the project, Leslie Groves, brought Truman a file full of reports and details on the Manhattan Project. They told Truman that although the U.S. was the only country with the resources to develop the bomb–eliminating fears that Germany was close to developing the weapon–the Russians could possibly have atomic weapons within four years. They discussed if, and with which allies, they should share the information and how the new weapon would affect U.S. foreign-policy decisions. Truman authorized the continuation of the project and agreed to form an interim committee that would advise the president on using the weapon.