when did washington become a state?
When did North Dakota South Dakota Washington and Montana become US states? North Dakota and South Dakota were admitted to the union on November 2, 1889 as the 39th and 40th states. Montana was admitted to the union on November 8, 1889 as the 41st. stâ¦ate. Washington was admitted to the union on November 11, 1889 as the 42nd state.