Congress created Dakota Territory, establishing a new federal territorial government that initially included today’s North and South Dakota and large parts of present-day Montana and Wyoming. This territorial framework set the stage for later Great Plains and Mountain West statehoods.
Congress organized Idaho Territory, a vast jurisdiction that initially included the areas that would become Idaho, Montana, and most of Wyoming. Subsequent territorial reorganizations carved new territories from it, shaping the pathway to multiple Mountain West states.
Congress created Montana Territory from Idaho Territory, reorganizing governance in the northern Rocky Mountains amid population growth and mining booms. This territorial creation was a key institutional step toward Montana’s later admission as a state.
President Abraham Lincoln issued the proclamation admitting Nevada to the Union. Nevada’s rapid admission during the Civil War made it one of the few states admitted during the conflict and added political support for the Union.
President Andrew Johnson issued a proclamation completing Nebraska’s admission to the Union, marking an early post–Civil War Great Plains statehood milestone and shrinking the remaining unincorporated federal territories in the region.
Congress created Wyoming Territory from parts of the Dakota, Idaho, and Utah Territories. This new territorial government formalized administration over a large Mountain West area and positioned Wyoming for eventual statehood.
Colorado entered the Union in the U.S. centennial year, earning the nickname “Centennial State.” Its admission represented a major step in consolidating federal control and state governance across the central Rockies.
Congress passed the Enabling Act of 1889, authorizing the people of Dakota Territory (to be divided into North and South Dakota), Montana Territory, and Washington Territory to form constitutions and state governments as a prerequisite to admission.
President Benjamin Harrison issued a proclamation admitting North Dakota as a state under the statehood process initiated by the Enabling Act of 1889, completing the transition from territorial governance to full representation.
President Benjamin Harrison issued a proclamation admitting South Dakota to the Union on the same date as North Dakota, finalizing the long-sought division of Dakota Territory into two states.
President Benjamin Harrison signed the formal proclamation admitting Montana to the Union, completing Montana Territory’s transition to statehood as part of the broader 1889 wave of admissions.
President Benjamin Harrison issued the proclamation declaring Washington a state, concluding Washington Territory’s statehood process after submission and certification of required documents.
Idaho joined the Union after its constitution was ratified and the admissions process advanced in Congress. Its admission further reduced the remaining Mountain West territories and expanded state governance in the interior Northwest.
President Benjamin Harrison issued a proclamation declaring Wyoming the 44th state. Wyoming’s admission capped a rapid sequence of late-19th-century statehoods that reshaped political representation across the Great Plains and Rockies.
President Grover Cleveland issued the proclamation admitting Utah to the Union, following Utah’s final constitutional convention and Congress’s acceptance of the state constitution.
After voters in Indian Territory and Oklahoma Territory approved statehood, President Theodore Roosevelt issued Presidential Proclamation 780 admitting Oklahoma as the 46th state, uniting the two territories into one state government.
New Mexico became the 47th state after a prolonged congressional and territorial process, completing one of the last major incorporations of continental U.S. territories into the Union.
President William Howard Taft issued the proclamation admitting Arizona to the Union as the 48th state, completing the last statehood admission in the contiguous United States.
Statehood of the Great Plains and Mountain States (1861–1912)
