16h 53min, aug 20, 1862 y - U.S.-Dakota War, Battles at Fort Ridgely
Dakota troops attack the fort twice-on Aug. 20 and Aug. 22. The fort, which had been a training base and planning base for Civil War volunteers, suddenly becomes one of the few military forts west of the Mississippi to defend a direct attack. Fort Ridgely’s 280 military and civilian defenders hold out until Army reinforcements end the attack.
Added to timeline:
Dakota War time line