The PSR has four Divisions which fill a map of the true Southwestern United States. We enjoy the Pacific Ocean to the West and the mountains to the East. The Los Angeles Division includes Ventura and Palmdale to the North and Claremont to the East. The Cajon Division includes the Chinook side of the Sierras; Orange, San Bernardino, and Riverside Counties in California; and Southern Nevada (Las Vegas). The San Diego Division covers the Southernmost part of California from the coast to the Colorado River. Last, the Arizona Division covers the state of Arizona. The area includes the lowest elevation in the US (- 248 feet MSL) and some of the highest in the 48 states. Mountains and deserts are common scenes in the undeveloped areas.

Before the railroad mergers, the area was served by Union Pacific, Southern Pacific, Santa Fe, and various small local rail carriers. The local museums maintain the history of cement, metal and coal mining, citrus groves, steel and aluminum smelting, cattle, lumber, aerospace, and hydroelectric development. All of these human activities included extensive use of rail services. Currently, the Port of Los Angeles and Long Beach serves as the major gateway to the Pacific Rim and thousands of rail containers are dispatched or received every day. Our geographic area includes Cajon Pass, and the major eastbound lines of the UP and BNSF railroads through Arizona.