HOW
From about 1811-1840 the Oregon Trail was laid down by traders and fur trappers. It could only be traveled by horseback or on foot. By the year 1836, the first of the migrant train of wagons was put together. It started in Independence, Missouri and traveled a cleared trail that reached to Fort Hall, Idaho.
Over the years, other wagon trains used West port, Leavenworth and St. Joseph as jumping-off points. The Apple gate train used Independence, preeminent since 1827 as an outfitting center. Since the majority of emigrants were farmers with families, they often chose Murphy farm wagons as their chief means of transport. Conestoga wagons, which weighed 1 1/2 tons empty, were too heavy for travel where there were no roads.
The Apple gate train began to assemble in late April, the best time to get rolling. The date of departure had to be selected with care. If they began the more than 2,000-mile journey too early in the spring, there would not be enough grass on the prairie to keep the livestock strong enough to travel. Animals would begin to sicken, slowing up the train. Such slowdowns would often throw off the schedule and sometimes cause major problems down the road. If they waited too long they might later be trapped in the mountains by early winter storms.
Brookes, Bob. “Oregon Trail.” HistoryNet, 2000, www.historynet.com/oregon-trail.