He had been commissioned by the Government to explore and report upon the country between the frontiers of Missouri and the South Pass in the Rocky mountains, on the line of the Kansas and Great Platte rivers.
Lieutenant Fremont had left Washington, and arrived at St.Louis on the twenty-second of May 1842.

Here he engaged a party of twenty-one men, principally Creole and Canadian boatmen, who were familiar with Indian life, having been long engaged in the service of the various fur companies.

In addition to these boatmen, Lieutenant Fremont had under his charge, Henry Brandt, nineteen years of age, son of Colonel J.B.Brant, of St.Louis, and Randolph Benton, a lively boy of twelve years, son of the distinguished U.S.Senator from Missouri.

These young men accompanied the expedition for that development of mind and body which their parents hoped the tour would give them.
With this party, Lieutenant Fremont was ascending the river four hundred miles, to the mouth of the Kansas, from which point he was to take his departure through the unexplored wilderness.

We say unexplored, though many portions of it had been visited by wandering bands of unlettered trappers and hunters.