[Fort Laramie] was one of the great fixed points of the later fur trade, in the heart of the Sioux country, on the way to the Shoshone country, linked to Bent’s Fort (Pueblo) by a well-traveled trail along the Laramie Fork and the Chugwater, linked to the lower Missouri posts by the great highway of the Platte valley.
Established in 1835 by William Sublette, it was first called Fort William for its builder. In 1841 the log fort was rebuilt of adobes on almost the same site and renamed Fort John, for John Sarpy, whom the Mormons knew as the friendly bourgeois of the American Fur Company post at Bellevue, below Winter Quarters. But not everyone called it Fort John. Most knew it as Fort Laramie, and literally everyone who traveled the Overland Trail knew it. Whether bound for Oregon, California, or the valleys of the mountains, whether traveling south bank or north, they had to come up the trough of the North Platte, and just at the bottleneck where the river emerged from rough country into the comparative open, there sat the fort on its barren gravel flat within a bright swift curve of the Laramie Fork, two miles above its junction with the North Platte.
Emigrants coming up the south bank forded the Laramie Fork to reach the fort, those coming up the North Platte forded or ferried the North Platte, depending on the season and the stage of water. From Fort Laramie onward to beyond South Pass, a distance of three hundred miles, the country cramped the several streams of the emigration into a single channel, at least at first. After 1850, when a way was opened along the north bank of the North Platte between the mouth of the Laramie Fork and the so-called Last Crossing (modern Casper, Wyoming), some trains, especially Mormon trains, elected to by-pass Fort Laramie. Their reasons were various—hurry because of lateness on the trail, fear of contamination by Gentile companies, unwillingness to pay bridge or ferry charges, or plain well-organized bull-headed self-sufficiency. But most, after weeks of plodding up the hot, dusty, treeless, brain-baking Platte valley, found the attractions of companionship, news, trail information, gossip, trade, repairs, and Taos Lightning more than mortal flesh cold resist even if it wanted to.