What was known as "The War Department" had a period of existence from August 7, 1789, in its early origins, it was also named the "War Office" during the revolution; and it was located in Philadelphia, and then moved to Washington D.C. in the early 1800s.
It was led by "The Secretary of War" who was member of the United States President's Cabinet, starting with George Washington's administration, until September 18, 1947. At this point, it got divided into Department of the Army and Department of the Air Force coming together to the Department of the Navy conforming the new "National Military Establishment" (NME), and in 1949 was renamed "the United States Department of Defense".
John Hancock, who was one of the wealthiest men in America at the time inherited his business from his uncle who was a mercantile businessman. He became a merchant, statesman, and served as a president of the Second Continental Congress amongst many other positions within that included Governor of Massachusetts.
The South reacted to the election of Abraham Lincoln by eventually seceding from the Union. This, of course, prefigured the Civil War