World War II, the deadliest military conflict in history, erupted in Europe on September 1, 1939, when Germany invaded Poland.

During World War II, navigating the Pacific Ocean's perilous tides and currents posed a constant challenge to the U.S. Navy. To update their maps and intelligence, the Navy established an Oceanographic Unit in 1943. The team of scientists was led by Mary Sears, a marine biologist commissioned as a lieutenant junior grade in the women’s division of the Naval Reserve, the WAVES.

After the Civil War, the federal government established a War Department agency to help Americans transition from slavery to freedom. The Freedmen’s Bureau (1865–72) issued rations, operated hospitals and helped establish schools and unite families. It worked to resolve labor disputes and negotiate labor contracts. It also presided over and documented marriages between freed couples.

From George Washington’s second term through Franklin D. Roosevelt’s first, inauguration day was generally held on March 4. Without cars or computers, the four months between the election and inauguration served a purpose in the late 18th and 19th centuries. It allowed the President-elect time to settle their affairs and journey to the nation’s capital.

This holiday featured film is one of a series of silent movies produced by the Post Office Department in 1921. The mini melodrama shows how the postal service helps make a happy Christmas for a boy and his sister when their “Dere Sandy Claws” letter is answered by a young married couple.