Samuel Phillips Lee was an officer of the United States Navy. In the American Civil War, he took part in the New Orleans campaign before commanding the North Atlantic Blockading Squadron, covering the coastlines and inland waters of Virginia and North Carolina, and finally the Mississippi River Squadron. As a cousin of Robert E. Lee, his refusal to join the Confederates' side by remaining loyal to the U.S. demonstrated how the war had divided families. Lee married Elizabeth Blair the daughter of Francis P. Blair Sr., and their house in Washington is now the president's official guest house.

The Union blockade in the American Civil War was a naval strategy by the United States to prevent the Confederacy from trading.