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

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

near the

Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid drainage basin, watershed that encompasses parts of ...

and is on the west and northwest border of the

Kofa National Wildlife Refuge The Kofa National Wildlife Refuge is located in Arizona in the southwestern United States, northeast of Yuma and southeast of Quartzsite. The refuge, established in 1939 to protect desert bighorn sheep, encompasses over of the Yuma Desert re ...

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

Dome Rock Dome Rock is an andesite formation of the Old Cascades in the Willamette National Forest. The mountain is best known for its hiking trail that goes to the summit. Dome Rock lies in Linn County, Oregon. About 3 miles southeast of Dome Rock is the ...

and

Trigo Mountains The Trigo Mountains are a north-south trending mountain range in La Paz County, Arizona, bordering the Colorado River on the east in the Lower Colorado River Valley. The range lies north of the Colorado River as it turns east, north of Martin ...

Quartzsite, Arizona Quartzsite is a town in La Paz County, Arizona, United States. According to the 2020 census, the population was 2,413. Interstate 10 runs directly through Quartzsite which is at the intersection of U.S. Route 95 and Arizona State Route 95 with ...

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

Interstate 10 Interstate 10 (I-10) is the southernmost cross-country highway in the American Interstate Highway System. I-10 is the fourth-longest Interstate in the United States at , following I-90, I-80, and I-40. This freeway is part of the originally pl ...

and

U.S. Route 95 US Route 95 (US 95) is a major north–south United States Numbered Highways, US Highway in the western United States. It travels through the states of Arizona, California, Nevada, Oregon, and Idaho, staying inland from the Pacific Coast ...

. The Plomosa, New Water and Kofa ranges border to the east. To the south the plain terminates at a drainage divide between the

Castle Dome Mountains The Castle Dome Mountains (Tolkepaya Yavapai: Wi:hopuʼ) 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 butte and distinctive landmark. The p ...

to the southeast and the

Chocolate Mountains The Chocolate Mountains of California are located in Imperial County, California, Imperial and Riverside County, California, Riverside counties in the Colorado Desert of Southern California. The mountains stretch more than 60 miles (100 km) ...

to the southwest.''Arizona Atlas and Gazetteer,'' plates 54 & 46, DeLorme, 2001, The northern reaches of the plain is crossed by the

Bouse Wash Bouse Wash is one of the larger eastern-bank dry washes that enter the Colorado River in the Lower Colorado River Valley. It is located in La Paz County, extreme western Arizona. Geography Bouse Wash is located on the north rim of the La Posa P ...

west of

Bouse Bouse ( ''rhymes with "house"'') is a census-designated place (CDP) and ghost town in La Paz County, Arizona, United States. Founded in 1908 as a mining camp, the economy of Bouse is now based on tourism, agriculture, and retirees. The populati ...

and extends on to east of

Parker Parker may refer to: Persons * Parker (given name) * Parker (surname) Places Place names in the United States *Parker, Arizona *Parker, Colorado * Parker, Florida * Parker, Idaho * Parker, Kansas * Parker, Missouri * Parker, North Carolina *Park ...

, terminating along the

Cactus Plain Cactus Plain is a plain east of the Colorado River and Parker Valley, in La Paz County, western Arizona, United States. Geography Cactus Plain is a landform within the Lower Colorado River Valley. It is adjacent to Bouse Wash, which is on the sou ...

south of the

Buckskin Mountains The Buckskin Mountains is a mountain range in La Paz County, Arizona, United States. The range lies just east of the north–south Colorado River, and borders south of the east–west, west-flowing Bill Williams River. Description The range is ...

Arizona State Route 72 State Route 72 (SR 72) is a state highway in the U.S. state of Arizona. It runs from SR 95 near Parker southeast to U.S. Route 60 (US 60) in Hope. Along its route in La Paz County, the highway is mostly parallel to the Arizona and California ...

crosses the plain between Bouse and Parker. File:Quartzsite, Arizona, seen from the air.jpg, Quartzsite, Arizona & southern La Posa Plain, looking north downhill on the La Posa Plain. The mountain range at the west (left) is the

Dome Rock Mountains The Dome Rock Mountains are a mountain range in southern La Paz County, Arizona. The range borders the Colorado River on the west and the Colorado River Indian Reservation on the northwest located in the Lower Colorado River Valley. Quartzsite, ...

References

* California Road and Recreation Atlas, 2005, p. 114 {{Authority control Plains of Arizona Landforms of La Paz County, Arizona Landforms of Yuma County, Arizona Sonoran Desert