The La Posa Plain is a wide, generally flat plain in western Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

 near the Colorado River

Colorado River

The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...

 and is on the west and northwest border of the Kofa National Wildlife Refuge

Kofa National Wildlife Refuge

The Kofa National Wildlife Refuge is located northeast of Yuma, Arizona, southeast of Quartzsite, Arizona, in the southwestern United States. The refuge, established in 1939 to protect Desert Bighorn Sheep, encompasses over of the Yuma Desert region of the Sonoran Desert...

. The plain lies to the east of the Colorado River Indian Reservation

Colorado River Indian Reservation

The Colorado River Indian Reservation is 189 miles west of Phoenix, Arizona, on highway 95. It lies in western La Paz County, Arizona, southeastern San Bernardino County, California, and northeastern Riverside County, California. It has a total land area of 432.22 sq mi , and most of it lies...

 and east of the Dome Rock

Dome Rock Mountains

The Dome Rock Mountains are a regionally short mountain range in southwestern Arizona in southern La Paz County. The range borders the Colorado River– on the west and also the southern section of the Colorado River Indian Reservation on the northwest located in the Lower Colorado River Valley...

 and Trigo Mountains

Trigo Mountains

The Trigo Mountains is a north-south trending mountain range, bordering the Colorado River on the east in the Lower Colorado River Valley and lies north of the Colorado River as it turns east, north of Martinez Lake and the Imperial Reservoir...

. Quartzsite, Arizona

Quartzsite, Arizona

Quartzsite is a town in La Paz County, Arizona, United States. According to Census Bureau estimates, the population of the town was 3,397 in 2006.Interstate 10 runs directly through Quartzsite. It is at the intersection of U.S...

 lies on the western part of the plain, which crosses both Interstate 10

Interstate 10 in Arizona

In the U.S. state of Arizona, Interstate 10, the major east–west Interstate Highway in the southern United States, runs east from California, enters Arizona and continues through Phoenix and Tucson and exits at the border with New Mexico.-Route description:...

 and U.S. Route 95.

The Plomosa

Plomosa Mountains

The Plomosa Mountains are a mountain range in La Paz County, Arizona, running generally south of Bouse, Arizona near the Arizona/California border. The maximum height of the range is 1791 feet ....

, New Water

New Water Mountains

The New Water Mountains is a mountain range in southwestern Arizona. The range is on the northern border of the Kofa National Wildlife Refuge as well as the northern Kofa Mountains.It is a northwest-southeast trending range, about 20 miles long...

 and Kofa

Kofa Mountains

The Kofa Mountains is the central mountain range comprising the Kofa National Wildlife Refuge, about 60 miles northeast of Yuma, Arizona in the southwestern part of the state...

 ranges border to the east. To the south the plain terminates at a drainage divide between the Castle Dome Mountains

Castle Dome Mountains

The Castle Dome Mountains are a mountain range in Yuma County, Arizona, within the Kofa National Wildlife Refuge. Castle Dome peak, the high point of the range, is a prominent and distinctive landmark. The peak is high, and is located at . Castle Dome was named by American soldiers at old Fort...

 to the southeast and the Chocolate Mountains

Chocolate Mountains (Arizona)

The Chocolate Mountains of Arizona are located in the southwestern part of the state east of the Trigo Mountains and southwest of the Kofa National Wildlife Refuge. The mountains are located about 30 miles east of the Chocolate Mountains of California, but the two ranges are not connected. The...

 to the southwest.

The northern reaches of the plain is crossed by the Bouse Wash

Bouse Wash

Bouse Wash is one of the larger eastern-bank dry washes that enter the Colorado River in western Arizona.Bouse Wash is located on the north end of the La Posa Plain and drains into the area along the Colorado River occupied by the Colorado River Indian Reservation, south of Parker, Arizona...

 west of Bouse and extends on to east of Parker

Parker, Arizona

Parker is a town in and the county seat of La Paz County, Arizona, United States, on the Colorado River in Parker Valley. The population was 3,140 at the 2000 census.-History:...

 terminating along the Cactus Plain

Cactus Plain

The Cactus Plain is a plain east of Parker, Arizona and the Parker Valley within the Lower Colorado River Valley.The Cactus Plain is adjacent to the Bouse Wash on the south, which drains northwest-west into the Colorado River...

 south of the Buckskin Mountains

Buckskin Mountains

The Buckskin Mountains are a mountain range in western-central Arizona, USA. The range lies just east of the north-south Colorado River, and borders south of the east-west, west-flowing Bill Williams River....

. Arizona State Route 72 crosses the plain between Bouse and Parker.