As the years passed, the Oregon Trail became a heavily used corridor from the Missouri River to the Columbia River. Offshoots of the trail continued to grow as gold and silver discoveries, farming, lumbering, ranching, and business opportunities resulted in much more traffic to many areas. Traffic became two-directional as towns were established along the trail. By 1870 the population in the states served by the Oregon Trail and its offshoots increased by about 350,000 over their 1860 census levels. With the exception of most of the 180,000 population increase in California, most of these people living away from the coast traveled over parts of the Oregon Trail and its many extensions and cutoffs to get to their new residences.