Yuma County is one of four original counties designated by the first Territorial Legislature. It maintained its original boundaries until 1983 when voters decided to split Yuma County into LaPaz County in the north and a new "Yuma County" in the south. For many years, Yuma served as the gateway to the new western territory of California, which brought thousands from around the world in search of gold, or those who had it. In 1870, the Southern Pacific Railroad bridged the river. Yuma became a hub for the railroad and was selected as the county seat in 1864.Yuma County is bordered by California on the West/Mexico on the South and has a year-round population of approximately 200,000 residents. During the winter, the population increases by about 90,000 due to the sun-seeking Winter Visitors affectionately known as "Snowbirds".