The most significant railroad serving El Paso was Southern Pacific. El Paso Union Station was controlled by Tower 196. At Tower 47, 2 miles east of Union Station, was the junction of SP's Valentine Subdivision towards Houston and New Orleans (Sunset Route), and the Carrizozo Subdivision towards Tucumcari, connecting with the Rock Island line to Kansas City and Chicago (Golden State Route). West of El Paso, SP's Lordsburg Subdivision extended west towards Tucson and Los Angeles. Amtrak continues to operate between New Orleans and Los Angeles. Texas & Pacific had trackage rights via SP's Valentine Subdivision 90 miles east to Sierra Blanca, where T&P's own main continued east to Fort Worth, Dallas and Texarkana. Santa Fe had a secondary line extending north of El Paso to Albuquerque. And the National Railways of Mexico connected El Paso with Mexico City, although the information available on the internet is vague regarding the exact routing across the border into Ciudad Juarez.
Throughout Texas, interlocking towers were assigned numbers, in the order in which they were registered with the Railroad Commission of Texas. Further information is at the Texas Railroad Interlocking Tower Web Site.