The first entity called Laramie County, meanwhile, was created by the legislature of the Dakota Territory on Jan. 8, 1867. It encompassed the entire area that later became the territory and state of Wyoming, except for a triangle-shaped area west of the Continental Divide and north of present-day Sweetwater County. The county seat was Fort Sanders, near present Laramie, Wyo.

Next, the Dakota Legislature took the western half of Laramie County and created Carter County, later renamed Sweetwater County, and on Jan. 3, 1868 moved the Laramie County seat to Cheyenne. During the following legislative session, Dakota lawmakers carved two more counties out of Laramie County: Albany and Carbon.

Thus, when Wyoming Territory was organized on May 19, 1869 with its capital at Cheyenne, Dakota lawmakers had already broken the area into four counties, and they became the first four counties of the new territory. The 1869 Territorial census reported 2,665 residents in Laramie County, with 2,305 in Cheyenne and 360 in Camp Carlin/Fort D. A. Russell.

Like the other earliest counties, Laramie County extended from the southern to the northern borders of the territory. In 1875, the Wyoming Legislative Assembly began creating new counties out of northern Laramie County. The Legislature authorized formation of Crook County in 1875, and a Crook County government was finally organized in 1885. Converse County was authorized in 1888, two years before Wyoming became a state. In 1911, the Legislature finished carving up the original Laramie County when it authorized formation of Platte and Goshen counties.

In 1886, meanwhile, Laramie and Albany counties dominated the Legislative Assembly, totaling seven members in the 12-member upper house and 13 in the 24-member lower house. They cooperated on legislation to build the Wyoming Capitol in Cheyenne and the University of Wyoming in Laramie.