Before the end of that time, the old yearning for the mountains, prairies and streams of the West came back to him, and he engaged passage on a steamer up the Missouri.
On the same boat John C.Fremont was a passenger.

He was two years younger than Carson and had been commissioned Second Lieutenant in the Corps of Topographical Engineers, in 1838.

Four years later he projected a geographical survey of the entire territory of the United States from the Missouri River to the Pacific.
Carson was attracted by the fine, manly and intellectual appearance of Fremont, and, learning he was in search of a skilful mountaineer, he introduced himself, referring in a modest fashion to his experience in the west and expressing the belief that he could be of service to the explorer.
Fremont was an excellent judge of character and was favorably impressed with Carson from the first.

The answers to the inquiries which he made concerning the famous guide and mountaineer, were satisfactory in the highest degree.

He engaged Carson as his guide, agreeing to pay him a salary of one hundred dollars a month.
The party of explorers were mainly gathered in St.Louis.It was composed mostly of Creole and Canadian voyageurs, Charles Preuss, a learned German, a young son of Colonel Benton (which statesman was the father in law of Fremont), several other friends, including a noted mountaineer named Maxwell, who was employed as the hunter of the party.
Including the commander, the entire company numbered twenty-eight.
With this party of explorers Fremont ascended the Missouri until the mouth of the Kansas was reached, when they disembarked and made their preparations for the long and dangerous journey before them.