1880s
- March 28, 1882
The part of Dakota Territory south of 43° north and north of the Keya Paha and Niobrara Rivers was transferred to Nebraska.
- May 17, 1884
The Department of Alaska, previously under the direct control of the federal government and the military, was redesignated the District of Alaska, forming a local government.
- November 2, 1889
Dakota Territory was split in two, and it was admitted as the 39th state, North Dakota, and 40th state, South Dakota.
- November 8, 1889
Montana Territory was admitted as the 41st state, Montana.
- November 11, 1889
Washington Territory was admitted as the 42nd state, Washington.
Read more about this topic: Territorial Evolution Of The United States