Given the remoteness and inaccessibility of the region, the Yokuts remained largely isolated from further contact until after the Mexican War of Independence, when Mexican settlers began to migrate to the area. Following the discovery of gold in California in 1848, settlers flooded into the San Joaquin Valley. In 1851, gold was discovered along the Kern River in the southern Sierra Nevada, and in 1865, oil was discovered in the valley. The Bakersfield area, once a tule reed-covered marshland, was first known as Kern Island to the handful of pioneers, who built log cabins there in 1860. The area was subject to periodic flooding from the Kern River, which occupied what is now the downtown area, and experienced outbreaks of malaria.