La Paz County is a county in the western part of the U.S. state of Arizona. As of the 2010 census, its population was 20,489. The county seat is Parker. The name of the county is the Spanish word for the peace, and is taken from the early settlement (now ghost town) of La Paz along the Colorado River.
La Paz County was established in 1983 after voters approved separating the northern portion of Yuma County, making it the first and only county to be established after Arizona became a state in 1912. The county did not have a large enough tax base to begin supporting a separate county government immediately and had to rely on state money at first. As a result Arizona laws were changed to make splitting other existing counties much more difficult.
The Colorado River Indian Reservation is located in the western portion of the county. Part of the reservation extends westward into San Bernardino and Riverside Counties in California.