When explorers, early trappers, hunters, and gold miners visited and settled in Colorado, the state was populated by American Indian nations. Westward expansion brought European settlers to the area and Colorado's recorded history began with treaties and wars with Mexico and American Indian nations to gain territorial lands to support the transcontinental migration. In the early days of the Colorado gold rush, Colorado was a Territory of Kansas and Territory of Jefferson. On August 1, 1876, Colorado was admitted as a state, maintaining its territorial borders.