Born in Madison County, Kentucky, near the city of Richmond, in 1811 Carson moved at the age of one year with his parents and siblings to a rural area near Franklin, Missouri. Carson's father, Lindsey Carson, was a farmer of Scots-Irish descent, who had fought in the Revolutionary War under General Wade Hampton. There were a total of 15 Carson children: five by Lindsey Carson's first wife, and ten by Kit's mother, Rebecca Robinson. Kit was the eleventh child in the family. The Carson family settled on a tract of land owned by the sons of Daniel Boone, who had purchased the land from the Spanish prior to the Louisiana Purchase. The Boone and Carson families became good friends, working, socializing, and intermarrying.
Carson was eight years old when his father was killed by a falling tree while clearing land. Lindsey Carson's death reduced the Carson family to a desperate poverty, forcing young Kit to drop out of school to work on the family farm, as well as engage in hunting. At age 14, Kit was apprenticed to a saddlemaker (Workman's Saddleshop) in the settlement of Franklin, Missouri. Franklin was situated at the eastern end of the Santa Fe Trail, which had opened two years earlier. Many of the clientele at the saddleshop were trappers and traders, from whom Kit heard stirring tales of the Far West. Carson is reported to have found work in the saddle shop suffocating: he once stated "the business did not suit me, and I concluded to leave". His master may have agreed with his leaving since he offered the odd amount of 1 cent for his return and waited a month to post the notice in the local newspaper.
At sixteen, Carson secretly signed on with a large merchant caravan heading to Santa Fe. His job was to tend the horses, mules, and oxen. During the winter of 1826-1827 he stayed with Matthew Kinkead, a trapper and explorer, in Taos, New Mexico, then known as the capital of the fur trade in the Southwest. Kinkead had been a friend of Carson's father in Missouri, and he taught Carson the skills of a trapper. Carson also began learning the necessary languages. Eventually he became fluent in Spanish, Navajo, Apache, Cheyenne, Arapaho, Paiute, Shoshone, and Ute.
 The trapper years (1829-40)
See Fur trade
After gaining experience along the Santa Fe Trail and in Mexico, Carson signed on with a trapping party of forty men, led by Ewing Young in the Spring of 1829. This was Carson's first official expedition as a trapper. The journey took the band into unexplored Apache country along the Gila River. Ewing's group was approached and attacked by Apache natives. It was during this encounter that Carson shot and killed one of the attacking Apache, the first time he killed a man.
At the age of 25, in the summer of 1835, Carson attended an annual mountain man rendezvous, which was held along the Green River in southwestern Wyoming. He became interested in an Arapaho woman whose name, Waa-Nibe, is approximated in English as "Singing Grass" Her tribe was camped nearby the rendezvous. Singing Grass is said to have been popular at the rendezvous and also to have caught the attention of a French-Canadian trapper, Joseph Chouinard. When Singing Grass chose Carson over Chouinard, the rejected suitor became belligerent. Chouinard is reported to have thrown a fit, disrupting the camp to the point where Carson could no longer tolerate the situation. Words were exchanged, and Carson and Chouinard charged each other on horses while brandishing their weapons. Using a pistol, Carson blew off Chouinard's thumb. His opponent barely missed killing Carson with his rifle shot; it grazed below his left ear and scorched his eye and hair. Carson said that the fact that Chouinard's horse shied probably saved him, as Chouinard was a splendid shot.
Controversy regarding Chouinard's fate continues. The duel with Chouinard is said to have made Carson famous among the mountain men but was also considered uncharacteristic of him.
Carson considered his years as a trapper to be "the happiest days of my life." Accompanied by Singing Grass, he worked with the Hudson's Bay Company, as well as the renowned frontiersman Jim Bridger, trapping beaver along the Yellowstone, Powder, and Big Horn rivers. They trapped throughout what is now Colorado, Utah, Wyoming, Idaho, and Montana. Carson's first child, a daughter named Adeline, was born in 1837. Singing Grass gave birth to a second daughter but developed a fever shortly after the birth, and died sometime between 1838-40.
At this time, the nation was undergoing a severe depression (see Panic of 1837). The fur industry was undermined by changing fashion styles: a new demand for silk hats replaced the demand for beaver fur. Also, the trapping industry had devastated the beaver population. This combination of facts ended the need for trappers. Carson said, "Beaver was getting scarce, it became necessary to try our hand at something else."
He attended the last mountain man rendezvous, held in the summer of 1840 (again at Ft. Bridger near the Green River) and moved on to Bent's Fort, finding employment as a hunter. Carson married a Cheyenne woman, "Making-Our-Road", in 1841. She left him only a short time later to follow her tribe's migration.
By 1842 Carson met and became engaged to the daughter of a prominent Taos family: Josefa Jaramillo. After receiving instruction from Padre Antonio José Martínez, he was baptized into the Catholic Church in 1842. At 34, Carson married his third wife, 14-year-old Josefa, on February 6, 1843. They had eight children together, the descendants of whom remain in the Arkansas Valley of Colorado.
 Guide with Fremont (1842-1846)
Carson decided early in 1842 to return to Missouri, taking his daughter Adeline to live with relatives near Carson's former home of Franklin, to provide her with an education. That summer he met John C. Frémont on a Missouri River steamboat. Frémont was preparing to lead his first expedition and was looking for a guide to take him to South Pass on the Continental Divide. As the two men became acquainted, Carson offered his services, as he had spent much time in the area. The five-month journey, made with 25 men, was a success, and Fremont's report was published by Congress. His report "touched off a wave of wagon caravans filled with hopeful emigrants" heading West.
Frémont's success in the first expedition led to his second expedition, undertaken in the summer of 1843. He proposed to map and describe the second half of the Oregon Trail, from South Pass to the Columbia River. Due to Carson's proven skills as a guide, Fremont invited him to join the second expedition. They traveled along the Great Salt Lake into Oregon. They determined that all the land in the Great Basin (centered on modern-day Nevada) was land-locked, which contributed greatly to the understanding of North American geography at the time. Farther west, they came within sight of Mount Rainier, Mount Saint Helens, and Mount Hood.
One goal of the expedition had been to locate the Buenaventura River, what was believed to be a major east-west river connecting the Great Lakes with the Pacific Ocean. Though its existence was accepted as scientific fact at the time, it was not to be found. Frémont's second expedition established that the river was a fable.
The second expedition became snowbound in the Sierra Nevadas that winter. Carson's wilderness skills averted mass starvation. Food was so scarce that their mules "ate one another's tails and the leather of the pack saddles."
The expedition moved south into the Mojave Desert, enduring attacks by Natives, who killed one man. When the expedition ventured into California, they crossed into Mexican territory. The threat of military intervention by that country sent Fremont's expedition southeast, into Nevada, to a watering hole known as Las Vegas. The party traveled on to Bent's Fort. By August 1844 they returned to Washington, over a year after their departure. Congress published Fremont's report on his expedition in 1845. It added to the national reputations of the two frontiersmen.
Along the route, Frémont and party came across a Mexican man and a boy who were survivors of an ambush by a band of Natives. They had killed two men, staked two women to the ground and mutilated them, and stolen 30 horses. Carson and fellow mountain man Alex Godey took pity on the two survivors. They tracked the Native band for two days, and upon locating them, rushed into their encampment. They killed two Native Americans, scattered the rest, and returned to the Mexicans with the horses."More than any other single factor or incident, [the Mojave Desert incident] from Frémont's second expedition report is where the Kit Carson legend was born....."
On June 1, 1845, John Frémont and 55 men left St. Louis, with Carson as guide, on the third expedition. The stated goal was to "map the source of the Arkansas River", on the east side of the Rocky Mountains. But upon reaching the Arkansas, Frémont suddenly made a hasty trail straight to California, without explanation. Arriving in the Sacramento Valley in early winter 1846, he sought to stir up patriotic enthusiasm among the United States immigrants there. He promised that if war with Mexico started, his military force would "be there to protect them." Frémont nearly provoked a battle with Mexican General José Castro near Monterey, Caliifornia. His troops so outnumbered the US expedition that they could likely have destroyed it. Frémont fled Mexican-controlled California, and went north to Oregon, making camp at Klamath Lake.
On the night of May 9, 1846, Frémont received a courier, Lieutenant Archibald Gillespie, bringing messages from President James Polk. Reviewing the messages, Frémont neglected the customary measure of posting a watchman for the camp. The neglect of this action is said to have been troubling to Carson, yet he had "apprehended no danger". Later that night Carson was awakened by the sound of a thump. Jumping up, he saw his friend and fellow trapper Basil Lajeunesse sprawled in blood. He sounded an alarm and immediately the camp realized they were under attack by Native Americans, estimated to be several dozen in number. By the time the assailants were beaten off, two other members of Frémont's group were dead. The one dead attacker was judged to be a Klamath Lake Native. Frémont's group fell into "an angry gloom." Carson was furious and smashed the dead warrior's face into a pulp.
To avenge the deaths, Frémont attacked a Klamath Tribe fishing village named Dokdokwas, at the junction of the Williamson River and Klamath Lake, on May 10, 1846. Accounts by scholars vary, but they agree that the attack completely destroyed the village structures; Sides reports the expedition killed women and children as well as warriors. Later that day, Carson was nearly killed by a Klamath warrior when his gun misfired as the warrior drew a poison arrow. Frémont trampled the warrior with his horse and saved himself."The tragedy of Dokdokwas is deepened by the fact that most scholars now agree that Frémont and Carson, in their blind vindictiveness, probably chose the wrong tribe to lash out against: In all likelihood the band of native Americans that had killed [Frémont's three men] were from the neighboring Modocs....The Klamaths were culturally related to the Modocs, but the two tribes were bitter enemies."
Turning south from Klamath Lake, Frémont led his expedition back down the Sacramento Valley, and promoted the Bear Flag Revolt, an insurrection of United States immigrant settlers. He took charge of it once it had adequately developed. When a group of Mexicans murdered two American rebels, Frémont imprisoned José de los Santos Berreyesa, the alcalde, or mayor of Sonoma, two other Berreyesa brothers, and others he believed were involved.
On June 28, 1846, Berreyesa's father, José de los Reyes Berreyesa, crossed the San Francisco Bay and landed near San Quentin with two cousins, twin sons of Francisco de Haro, to visit his sons in jail. Frémont ordered Carson and two others to execute the three Californios. Later, Carson told Jasper O'Farrell that he regretted killing the men, but that the act was only one such that Frémont ordered him to commit.