Leaving Missouri in 1824, William Ashley led a large group of men west in search of beaver. Ashley and his crew reached the banks of the Green River, then called Seeds-ke-dee, on April 9th, 1825 near the mouth of the Big Sandy River north of here. The men split into four groups to explore the area for beaver. Ashley oversaw the building of bull boats, clumsy craft made of buffalo hides stretched over willow frames, and then led seven men down the Green River on the first recorded river trip on that river. The party passed Expedition Island on Sunday, April 25, 1825, walked around many rapids including Ashley Falls, now under Flaming Gorge Reservoir, and continued through the Green's canyons until reaching the Uinta Basin, now Utah, on June 16th. Ashley then left the river and returned to this area for the first of the great annual rendezvous held on Henry's Fork in July 1825. Although news of Ashley's descent of the river was not widespread, it gradually spread in the States and showed others that travel down the Green River was possible. Later mountain men floated the Green in dugout canoes made from cottonwood logs.