Romania and Bulgaria signed the European Union’s Treaty of Accession, the last step to joining the Union.
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Francis Crick & James Watson's discovery of the double-helix structure of DNA was formally announced.
New York state became the first to require license plates on automobiles.
Porsche was officially added to the commercial register in Germany.
The Thornton Affair, a skirmish between American and Mexican soldiers in Texas, started a chain of events that led to the Mexican-American War.
President Harry Truman opened the two-lane White House bowling alley.
