The Dakota Territory consisted of the northern most part of the land acquired in the Louisiana Purchase
of the United States.
Most of Dakota Territory was formerly part of the Minnesota and Nebraska territories.
When Minnesota became a state in 1858, the leftover area between the Missouri River and
Minnesota's western boundary fell unorganized.
When the Yankton Treaty was signed later that year, ceding much of what had been Lakota land
to the U.S. Government, early settlers formed an unofficial provisional government and
unsuccessfully lobbied for United States territory status.
Then three years later President James Buchanan established the Dakota Territory, two days before Lincoln took the oath of office.
The territory included much of present-day Montana until 1864 and Wyoming until 1868.
The Territory of Dakota existed until November 2, 1889,
when that final extent of the territory was split and admitted to the Union as the states of North and South Dakota.