The Oregon Trail was one of the main overland migration routes on the North American continent, leading from locations on the Missouri River to the Oregon Territory. The eastern half of the trail was also used by travelers on the California Trail, Bozeman Trail and Mormon Trail which used much of the same trail before turning off to their separate destinations. To complete the journey in one traveling season most travelers left in April to May--as soon as grass was growing enough to support their teams and the trails dried out. To meet the constant needs for water, grass and fuel for campfires the trail followed various rivers and streams across the continent. In addition the network of trails required a minimum of road work to be made passable for wagons. They traveled in wagons, pack trains, on horseback, on foot, by raft and by boat to establish new farms, lives and businesses in the Oregon Territory. This territory in the early 19th century was initially jointly governed by both the United States and Britain. The four to six month journey spanned over half the continent as the wagon trail proceeded about 2,000 miles (3,200 km) west through territories and land later to become six U.S. states: Missouri, Kansas, Nebraska, Wyoming, Idaho, and Oregon. Extensions of the Oregon Trail were the main arteries that fed settlers into six more states: Colorado, Utah, Nevada, California, Washington, and Montana. Between 1841 and 1869 the Oregon Trail was used by settlers, ranchers, farmers, miners and business men migrating to the Pacific Northwest of what is now the United States. Once the first transcontinental railroad by the Union Pacific and the Central Pacific was completed in 1869, the use of this trail by long distance travelers rapidly diminished as the railroad traffic replaced most need for it. By 1883 the Northern Pacific Railroad had reached Portland, Oregon and most of the reason for the trail disappeared. Roads were built over or near most of the trail as local travelers traveled to cities originally established along the Oregon Trail.