Tower 112 to Centex, Track 2

Amtrak's Texas Eagle uses the former SP station in San Antonio (so it can connect with the Sunset Limited). With Union Pacific's acquisition of the M-K-T as well as the MoPac, it has chosen to operate the former M-K-T and former MoPac lines between San Antonio and Centex, just north of San Marcos, as paired track. The main connection with Track 2, the former MKT, is west of the former SP station, connecting at Tower 112. To use the connector at Tower 112, the first move of a northbound Texas Eagle (facing north in the station), and the last move of a southbound, must take place in reverse.  The former MKT line and the Sunset Route cross at grade east of the former SP station, but prior to the UP/SP merger there is no connection between the two lines there. This maneuver cost the Texas Eagle at least half an hour in running time, in each direction. The new connector makes it possible to leave the SP station heading north, to run via Track 2.

From Tower 112 (MP 259.8), the 40 mph, Track Warrant Control, Automatic Block Signals, line heads due east, while the Sunset Route turns away due north, with dual highway bridges overhead, east of Tower 112, a grade crossing, a cutting lines with trees, a road bridge overhead, and a bridge over drainage, and then turns north about two miles further east. After passing a bridge over drainage and a spot where the Galveston, Harrisburg & San Antonio once bridged overhead, the line passes beneath the former SP, and the post-merger connector from the Sunset Route trails in from the southwest, as the line turns north-northeast past a grade crossing, a highway bridge overhead, a grade crossing, a spur heading away east, a grade crossing with an angled street, and Travis (MP 254.3).

The line turns northeast, past a street alongside to the east, then a highway alongside to the east, with a drainage channel between the track and the highway, and then just east of north, past two grade crossings, a track diverging to the northeast, Remount (MP 250.7), a grade crossing, a bridge over an interstate highway and ramps, Fratt (MP 248.8), a bridge over a road, a grade crossing, a closed grade crossing, and Longhorn (MP 247.0), where a connector from the MP line (Track 1) once trailed in from the west, and then turns east, north, and northeast again, past a wide bridge overhead, a road alongside to the east, Intermediate Signals, a road bridge overhead, a detector at MP 243.6, an angled highway bridge overhead, Intermediate Signals, a bridge over a road, a grade crossing, Intermediate Signals and additional tracks at Instell (MP 238.6), a grade crossing, a bridge over a stream, additional track at Monotech (MP 238.4) and at Custom Brick (MP 237.1) to North Schertz (MP 236.9), where a connector trails in from South Schertz on Track 1 and single track, CTC, replaces the TWC, ABS, additional track at Universal Forest products (MP 236.7) and Ogden Junction (MP 235.9), where a connector heads north to Craig Junction on Track 1.

The countryside north of San Antonio is lush farmland, since it is (just) east of the 100th meridian that represents the general boundary between the arid land to the west and the lusher land to the east. Also along the railroad between San Antonio and San Marcos are a number of rock quarries providing the kind of rock used in railroad construction and maintenance, as well as road building. 

Track 2 continues past a narrow grade crossing, a road alongside to the east, an angled grade crossing, a narrow grade crossing, Intermediate Signals, Cornal, a dirt road grade crossing, two dirt track grade crossings, a gated grade crossing, a grade crossing, three dirt track grade crossings, Intermediate Signals, Solms, two grade crossings, a dirt road grade crossing, signals at Dittlinger (MP 231.1), where the Western Railroad trails in from the northwest, a grade crossing, a dirt road grade crossing, additional tracks at Brauntex (MP 230.8) and at McCoy Lumber (MP 229.5), a road bridge overhead, a grade crossing, Intermediate Signals, and three grade crossings, and turns north at a grade crossing at Landas Park (MP 227.8), where the speed limit falls to 25 mph, past two grade crossings and the flat crossing with Track 1 at New Braunfels (MP 227.0), where there is a connector in the northeast quadrant, rising again to 40 mph as the line turns northeast past a bridge over a street, a track trailing in on the east side, a through truss bridge over a river, a grade crossing into a golf course, an angled grade crossing, three grade crossings, a road bridge overhead, an angled grade crossing,  Gruene, Coleman (MP 223.9),a bridge over a river, a grade crossing, Intermediate Signals at MP 222.8, a detector at MP 221.4, an angled grade crossing, Conrads (MP 221.0), where the speed limit rises to 50 mph and there is a connector from Track 1, a connector over to Track 1 (MP 220.0), a grade crossing at Watson Lane, a through truss bridge over a river, two grade crossings, Jude (MP 219.0), where there is also a connector to Track 1, and Hunter (MP 217.4).

The speed limit falls to 40 mph as Track 2 jogs east-northeast to pass beneath a three arch bridge carrying Track 1 on an embankment, and resumes its northeastward heading past  a grade crossing, Jama (MP 213.5) to UP Junction (MP 212.0), where a connector heads off to Track 1, and a connector trails in from Track 1, and additional track at  Intermediate Signals at Southern Post Texas (MP 211.3), and to 30 mph past a grade crossing and the passenger station at San Marcos (MP 209.8), and Ajax MP 209.1), where the former MKT line turns away east and there is a connection north-northeast to Centex (MP 208.3), on the former MP line heading north-northeast from this point, where Track 1 trails in from the southwest.

Approaching San Marcos, up on the hill to the west is San Marcos State University, its new high rises overshadowing the original two-story brick buildings where LBJ went to college and performed chores for the college president in return for lodging and board.