Governor Stevens left Washington on May 9, 1853, for St. Louis, where he made arrangements with the American Fur Company to transport a large part of his supplies by river to Fort Union. From St. Louis he ascended the Mississippi by steamer to St. Paul, near which city Camp Pierce, his first organized camp, had been established. Here he issued his instructions and worked into shape his party,--to say nothing of his 172 half-broken mules. "Not a single full team of broken animals could be selected, and well broken riding animals were essential, for most of the gentlemen of the scientific corps were unaccustomed to riding." One of the engineers dislocated a shoulder before he conquered his steed. The party assigned to Governor Stevens's command was recruited with reference to the varied demands of a general exploring and scientific reconnaissance. Besides enlisted men and laborers, it included engineers, a topographer, an artist, a surgeon and naturalist, an astronomer, a meteorologist, and a geologist. Its two large volumes of report include elaborate illustrations and appendices on botany and seven different varieties of zoölogy in addition to the geographical details required for the railway. The expedition, in its various branches, attacked the northernmost route simultaneously in several places. Governor Stevens led the eastern division from St. Paul. A small body of his men, with much of the supplies, were sent up the Missouri in the American Fur Company's boat to Fort Union, there to make local observations and await the arrival of the governor. United there the party continued overland to Fort Benton and the mountains. Six years later than this it would have been possible to ascend by boat all the way to Fort Benton, but as yet no steamer had gone much above Fort Union. From the Pacific end the second main division operated. Governor Stevens secured the recall of Captain George B. McClellan from duty in Texas, and his detail in command of a corps which was to proceed to the mouth of the Columbia River and start an eastward survey. In advance of McClellan, Lieutenant Saxton was to hurry on to erect a supply depot in the Bitter Root Valley, and then to cross the divide and make a junction with the main party.