The main Oregon and California Trail went almost due north from Fort Bridger to the Little Muddy Creek where it passed over the Bear River Mountains to the Bear River Valley, which it followed northwest into the Thomas Fork area, where the trail crossed over the present day Wyoming line into Idaho. In the Eastern Sheep Creek Hills in the Thomas Fork valley the emigrants encountered Big Hill. Big Hill was a detour caused by a then-impassable cut the Bear River made through the mountains and had a tough ascent often requiring doubling up of teams and a very steep and dangerous descent. (Much later, US-30, using modern explosives and equipment, was built through this cut). In 1852 Eliza Ann McAuley found and with help developed the McAuley Cutoff which bypassed much of the difficult climb and descent of Big Hill. About on they passed present-day Montpelier, Idaho, which is now the site of the National Oregon-California Trail Center. The trail follows the Bear River northwest to present-day Soda Springs. The springs here were a favorite attraction of the pioneers who marveled at the hot carbonated water and chugging "steamboat" springs. Many stopped and did their laundry in the hot water as there was usually plenty of good grass and fresh water available. Just west of Soda Springs the Bear River turns southwest as it heads for the Great Salt Lake, and the main trail turns northwest to follow the Portneuf River valley to Fort Hall, Idaho. Fort Hall was an old fur trading post located on the Snake River. It was established in 1832 by Nathaniel Jarvis Wyeth and company and later sold in 1837 to the Hudson's Bay Company. At Fort Hall nearly all travelers were given some aid and supplies if they were available and needed. Mosquitoes were constant pests, and travelers often mention that their animals were covered with blood from the bites. The route from Fort Bridger to Fort Hall is about , taking nine to twelve days.