In 1859, a large party of gold-seekers led by Ruben Spalding discovered gold near the headwaters of the Blue River, which prompted a population surge in Summit County, Colorado. By October 1859, nearly 100 miners had camped along the river. By 1880, the human population of Summit county had swelled to 5,459. In 1881, Dillon Mining Company patented a 320-acre parcel and divided it into lots to establish the trade-post town of Dillon along the northeast bank of the Snake River, which is part of what was then called Blue River Valley. The town of Dillon was incorporated in 1883, but soon relocated to the west bank of the Blue River when Denver and Rio Grand Railroad came to Blue River Valley but had bypassed Dillon. Dillon was moved a second time in 1892 when the Denver, South Park and Pacific Railroad arrived from the northeast. The town was located at the confluence of three rivers: the Blue, Tenmile Creek and the Snake to provide one station for the two railroad lines. In 1890, Dillon's population was 133, less than 20% as large as Breckenridge at the time. Prior to its third move to the present location in 1961, the town had grown to 814 residents, the largest town in Summit County, however, most of this population consisted of construction workers for the dam.