Portal:Military of the United States/Selected anniversaries/March 31
- 1774 - American Revolutionary War: The Kingdom of Great Britain orders the port of Boston, Massachusetts closed in the Boston Port Act.
- 1854 - Commodore Matthew Perry signs the Treaty of Kanagawa with the Japanese government, opening the ports of Shimoda and Hakodate to American trade.
- 1992 - USS Missouri (BB-63), the last active US Navy Battleship, is decommissioned in Long Beach, California.
- 2004 - In Fallujah, Iraq, 4 American private military contractors working for Blackwater USA, are killed and their bodies mutilated after being ambushed.