Most of Jackson County is a high relatively broad intermontane basin known as North Park which covers 1613 square miles. This basin opens north into Wyoming and is rimmed on the west by the Park Range, on the south by the Rabbit Ears Range, and on the east by the Medicine Bow Mountains. Elevations ranges from 7,800 to 12,953 feet above sea level and is home to the head waters of the North Platte River. The term park is derived from parc, the French word for game preserve. At one time North Park was filled with herds of deer, antelope and buffalo. As a matter of fact there were so many buffalo in the area the Ute Indians gave North Park the name "Bull Pen". Now deer, elk and cattle vie for the same area.
One of the earliest occupants to the area were a people known as the Fremont Indians. Little is known about the Fremonts, but archaeological evidence suggest a hunting and gathering culture. They made their home in western Colorado from about A.D. 250 to about A.D. 1300, when they mysteriously abandoned the region. The Ute were next to occupy the area, moving into western and central Colorado sometime between 1300 and 1500. They were nomadic hunters. The arrival of the Spaniards introduced the horse to Native Americans and had a major influence on the Ute. The Ute were among the first North American Indian groups to use the horse, and quickly became excellent horsemen. The first Europeans to visit the area were French trappers in the late 1700's. In 1824-25, William Ashley, the founder of the Rocky Mountain Fur Trade Company, explored some of the area that later became the Colorado branch of the Overland Trail. An expedition led by Capt. John Charles Frémont in 1844, which went through North Park, produced the first detailed maps and drawings from the area. The gold rush of 1859 brought thousands of people to the Colorado area but few miners or settlers started showing up in North Park until the late 1870's.
The area which is now Jackson County was part of Spain from 1540 after the expedition of Francisco Vásquez de Coronado. Although he never entered Colorado and had no idea what lay there he none the less claimed all for Spain. In 1682 the French explorer René-Robert Cavelier, Sieur de La Salle, explored the Mississippi River. When he reached the mouth of the river he claimed all the land drained by the Mississippi for King Louis XIV, calling it Louisiana. It remained French until the 1763 Treaty of Paris ended the French and Indian War. France was forced to relinquish all holdings in North America to Great Britain except the land west of the Mississippi previously ceded to Spain, her ally. So once again Jackson County was under Spanish domain. In 1800 Napoleon forced Spain to return their portion of Louisiana to France. Then three years later, needing money, Napoleon sold Louisiana to America for $15 million dollars. Now for the first time Jackson County was under the domain of the United States. The western boundary was vague with both sides using different boundary markers. The Adams-Onis Treaty of 1819 took care of that setting the boundary as a line north of the headwaters of the Arkansas River. This left Jackson County divided between the United States and Spain, with Spanish territory west of the North Platte River. When Mexico gained independence in 1821 she inherited all Spanish territory in North America. Thus the land west of the North Platte River was now Mexican. The Mexican government like the Spanish never established forts or many permanent settlements to make a strong Mexican influence in the area. So when Texas revolted and gained independence from Mexico they claimed territory north and east of the Rio Grande River. Now the western part of Jackson County was Texan. Much of this claimed territory was disputed by Mexico, so when the United State annexed Texas she inherited these disputes. But that all ended with the treaty of Guadalupe-Hidalgo which ended the Mexican War. Mexico lost all land from the Rio Grande to California. So what is now Colorado was in United States territory.
The area that was to become Colorado was first divided up into four territories. These were Utah and New Mexico, created in 1850, and Kansas and Nebraska, created in 1854. So the area that was to become Jackson County was now in Nebraska Territory. Nebraska Territory didn't have much interest in the area and did not set up any counties. When settlers near Fort St. Vrain adopted the name of St. Vrain as its county and petitioned Nebraska Territory for this, they were largely ignored. In 1858 voters in the Colorado area lobbied for the establishment a new territory. When the Federal Government took no action the voters gathered again and voted for the new territory of Jefferson in October 1859. Although the territory was never recognized it helped pave the way for the creation of Colorado Territory in February 1861. It was named Colorado because the Republican congressmen were not about to name a territory after the founder of the Democratic Party.
In November of 1861 Colorado set up 17 counties for the state, with Larimer County as one of these. This was the county Jackson County would be carved out of in 1909. But before then both Grand and Larimer Counties claimed the North Park area. In the beginning no one paid much attention to North Park because it was the hunting grounds of the Ute and Arapaho Indians. They fiercely defended these lands and the white settlers were often afraid to venture in. When valuable minerals were discovered in North Park, Grand County claimed it as part of their county. They wanted the revenue it would provide for the county. The residents didn't care much because the county seat for Grand County was closer than the one in Larimer County, and all official business needed to be done at the county seat. But Larimer also claimed this county and it was contested all the way to the Colorado Supreme Court. In 1886 the court decided in favor of Larimer. This did not make the North Park residents very happy and they pushed for their own county until Jackson was formed.