Captain Bonneville made a camp at Chimney Rock, the height of which, according to his triangulation, was one hundred and seventy-five yards. On the 21st he made camp amidst the high and beetling cliffs, known a few years afterward as Scott's Bluffs.
The route of Captain Bonneville's march was generally along the bank of the Platte River, but frequently he was compelled, because of the steep bluffs which bounded it, to make inland detours.
In July he camped on a branch of the Sweetwater, which by measurement was sixty feet wide and four or five deep, flowing between low banks over a sandy soil. At that point numerous herds of buffalo were seen.
On the 12th of July, the caravan reached Laramie's Fork, and, abandoning the Platte, made a detour to the southwest. In two days afterward they camped on the bank of the Sweetwater. Up that stream they moved for several days, and on the 20th of July first caught a glimpse of the Rocky Mountains, which they crossed and then went on to the Pacific coast.
On the 13th of July of the following year after his tour through the Rocky Mountains, Bonneville arrived in the Green River Valley, which he now found covered in every direction with buffalo carcasses. It was evident that the Indians had recently been there and in great numbers. Alarmed at what he saw, the captain halted as soon as night came on, and sent out his scouts to the trappers' rendezvous at Horse Creek, where he expected to meet a party. When the scouts returned with some of the trappers, his mind was relieved by the information that the great slaughter of the buffaloes had been made by a band of friendly Shoshones.
The Green River Valley, at the time of Captain Bonneville's visit, was one of the general rendezvous of the trappers, traders, and Indians. There he got together a band of some of the most experienced men of the mountains, and determined to continue to explore into unknown regions farther west. His objective point was the Great Salt Lake, of which he had heard such wonderful accounts, and on the 24th of July he started from the Green River Valley with forty men to explore that inland sea.
In the spring of 1835 Captain Bonneville returned to the Green River Valley, and from there pursued his course down the Platte, reaching the frontier settlements on the 22d of August, having been absent over three years. During all that time he had made no report to the War Department, which thought he had perished on his venturesome journey, and his name was stricken from the rolls of the army. Several months after his arrival in Washington, and a satisfactory explanation having been rendered, he was restored to his position.[13]
On the 22d of May, 1842, Lieutenant John C. Fremont, of the United States Corps of Army Engineers, arrived at St. Louis in pursuance of orders from the War Department, to command an exploring expedition westward to the Wind River Mountains. On the 10th of June he started with the celebrated Kit Carson as his chief guide; his route was up the Kansas River to the Blue, thence across to the Platte, which he reached on the 25th. The principal object of his expedition was a survey of the North Fork of that river. He found the width of the stream, immediately below the junction of its two principal branches, to be 5350 feet. Hunting buffalo and an occasional Indian scare were the only important incidents of his march up the valley. The expedition returned by the same route and arrived at the mouth of the Platte on the 1st of October.
Before reaching Laramie's Fork, he met on the 28th of June a party of fourteen trappers, in the employ of the American Fur Company, making their way on foot with their blankets and light camp equipage on their backs. Two months previously they had started from the mouth of the Laramie River in boats loaded with furs destined for the St. Louis market. They had taken advantage of the June freshet, and were rapidly carried down as far as Scott's Bluffs. There the water spread out into the valley, and the stream was so shallow they were compelled to unload the principal part of their cargo. This they secured as well as possible, and left a few of their men to guard it. They continued struggling on with their boats in the sand and mud fifteen or twenty days longer, then, farther progress being impossible, they cached their remaining furs and property in trees on the bank of the river, and, each man carrying what he could on his back, started on foot for St. Louis. The party was entirely out of tobacco when they were met by Fremont, who kindly gave them enough to last them on their homeward journey.
During the next decade the Platte Valley witnessed a wonderful change. From the habitat of the lonely trapper, hunting on its many streams, it became the chosen route of a vast migration, seeking possession of the virgin soil of far-off Oregon, or attracted by the discovery of gold in California. The hegira of the Mormons to the sequestered basin of the Great Salt Lake also swelled the stream, and was followed soon after by the establishment of the overland stage, the pony express, and the building of the Union Pacific Railroad.