President Donald Trump banned transgender persons from joining the US military.
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Francisco Pizarro became the Governor of Castile, which is a historic area of modern-day Peru.
Platform diver Tom Daley won his first Olympic gold medal in men's synchronized diving, 13 years after his first Olympic games.
Albert Einstein's theory of gravitational redshift was proven after a telescope in Chile observed a black hole.
The Summer Olympic Games opening ceremony was held outdoors for the first time ever.
President Harry Truman signed the National Security Act.
