Between 1541 and 1739 explorers from Spain and France came to the area in search of gold, knowledge and trade with the Indians. In 1803, Kansas became a part of the United States as part of the Louisiana Purchase. Fifty-one years later it was organized as a territory which included the eastern half of Colorado.
Conflict over slavery led to bloody battles between free-staters (anti-slavery) and pro-slavery forces. This led to the attack on Lawrence by pro-slavery forces and the widespread public outcry associated with "Bleeding Kansas." Kansas became part of the United States as a free state in 1861.