The US Postal Service was founded.
Benjamin Franklin was named the first Postmaster General.
Source
President Harry Truman signed the National Security Act.
Albert Einstein's theory of gravitational redshift was proven after a telescope in Chile observed a black hole.
The opera 'Parsifal' by Richard Wagner premiered in Bayreuth, Germany.
As part of the War of the Roses in England, the Battle of Edgcote took place.
The Summer Olympic Games opening ceremony was held outdoors for the first time ever.
