The first structure at the Fort Laramie site was a cottonwood stockade, built in 1834 by William Sublette and his fur trade associates. According to an early visitor, it was square enclosure, approximately 150 feet on a side, with blockhouses above the gate and at diagonally opposite corners. Its design favored both trade and defense. Its location, near the confluence of the North Platte and Laramie Rivers and close to a trail frequented by trappers, made it a natural commercial site.
By 1836 Fort William had passed into the hands of the American Fur Company who developed it into a major center for the fur trade. The trade initially focused on beaver pelts that were used for making hats. Mountain men trapped the high country for beaver and traded the pelts for supplies to support their activities and for items of profit. As demand for beaver hats diminished, however, the trade shifted to bison robes. Bison robes were used as bedcovers, rugs, wall hangings, slave bedding, and lap blankets. They were produced, not by mountain men, but by Plains Indians.
In 1841 a rival fort, Fort Platte, was constructed only about a mile from Fort William. In response, the aging structure of Fort William was replaced by a new adobe fort called Fort John.
