Southern Pacific's Austin Subdivision extended east of Austin through Giddings to Hempstead, where it joined the SP main line to Houston from Dallas. At Pershing, 2 miles east of Austin, was a junction with SP's Llano Subdivision and the Missouri Kansas Texas line north to St. Louis. The MKT line paralleled the SP Austin Subdivision 3 miles further east, before turning north. SP discontinued passenger service on the Llano Subdivision in 1937, but commuter service was introduced in 2009.
The Missouri Pacific main line from Palestine to San Antonio and Laredo passed west of downtown Austin. East of the present Amtrak station and north of the Colorado River bridge was a wye known as Tower 205. And until 1947, when MP constructed a new station at the present Amtrak location, MP passenger trains served downtown Austin via a 1/2 mile spur east of Tower 205. A backup move was required. Also, Missouri Kansas Texas trains to San Antonio used trackage rights over MP to San Marcos, 30 miles south.
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.