The San Diego and Imperial Valley Railroad (SD&IV) is a class III railroad operating freight rail service in the San Diego area, providing service to customers in the region and moving railcars between the end of the BNSF Railway in Downtown San Diego and the Mexico–United States border in San Ysidro. The railroad has exclusive trackage rights to operate over tracks of the San Diego and Arizona Eastern Railway, a subsidiary of the Metropolitan Transit System, the regional public transit service provider. Tracks are shared with the San Diego Trolley, another subsidiary of the Metropolitan Transit System, and freight trains are only operated at night when passenger service is not in operation. The San Diego & Imperial Valley Railroad was established in October 1984 and is owned and operated by Genesee & Wyoming, a holding company that operates more than 100 shortline railroads like the SD&IV.

The Pacific Imperial Railroad was a company in possession of the SD&AE Desert Line right of way in Southern California, colloquially referred to as the Desert Line. The Desert Line starts at the border crossing at Division, near Campo at Milepost 59.94 in eastern San Diego County, California where it connects with the Baja California Railroad in Mexico, and stretches 70.1 miles through the Jacumba Mountains to El Centro, California, where it connects to Union Pacific Railroad at Milepost 129.61. The significance of the Desert Line is that it provides an alternative rail route to and from the east for servicing the distribution, transportation, and supply chain needs of the Cali-Baja region.