Texas Railroad History - Tower 5 - Houston

A Crossing of the Texas and New Orleans Railway and the San Antonio & Aransas Pass Railway

In 1876, the Texas Transportation Co. built tracks in Houston along the north bank of Buffalo Bayou between the community of Clinton (now known as Galena Park) and downtown. A few years later, these tracks came under Southern Pacific (SP) ownership and were assigned to its Texas & New Orleans (T&NO) subsidiary as the Clinton Branch. They proved valuable in serving port industries, particularly once the Houston Ship Channel was built.

The San Antonio & Aransas Pass (SA&AP) Railway entered Houston in 1888 from the west, crossing south of downtown and constructing a station at Polk Street. To access T&NO's Englewood Yard on the northeast side of Houston, SA&AP built an extension that bridged Buffalo Bayou and crossed T&NO's Clinton Branch a short distance beyond the north bank. On December 4, 1902, Tower 5 was authorized by the Railroad Commission of Texas (RCT) for operation at this crossing with a mechanical interlocker having 12 functions (four home signals, four distant signals and four derails). Initially, RCT listed Tower 5 as being in "East Houston" but this was subsequently changed to "East of Houston", a location that persisted through RCT's final interlocker list published in 1930.

Historic Map, Tower 5 Location

Above: The 1924 Sanborn map of Houston shows the T&NO Clinton Branch parallel to, and a short distance north of, Clinton Drive. It ran east / west along "Baron Drive" (which field examination suggests was never much of a street). The SA&AP crossed at Tower 5 running generally north / south, but as the map shows, the heading was really NNE / SSW at the diamond. Below: A magnification of the lower right area of the above image shows Tower 5 documented in the southwest quadrant of the crossing as a two-story "Off" [office] structure; both "Off" and the two stories imply that this was a regularly manned facility. The doorway was located on the south side of the building. The lack of a staircase marked externally implies that upper floor access was inside, perhaps a steep staircase or a ladder.


SP documents obtained by Carl Codney paint a complex picture of Tower 5's existence. Extracting all of the dates from these documents as well as dates from RCT information archived at DeGolyer Library yields the following timeline:

  1902, December 4 Tower 5 interlocking plant commissioned for operation by RCT
  1903, December 3 SP document Statement Showing Levers, Functions and Division of Expense at Interlocking Plant is created
  1903, December 31 Tower 5 listed in RCT annual report as a 12-function / 12-lever mechanical interlocking plant
  1907, June 28 SP interlocking plan D-402 is issued (unknown implication; perhaps the original plan drawing had never been formally "released" by SP's Engineering Dept.?)
  1916, August Statement Showing Levers, Functions and Division of Expense at Interlocking Plant is "checked"
  1918, November 17 "temporarily placed out of service at 6 PM" (no reason specified)
  1920, March 5 "placed back in service"
  1925, July 11 "placed out of service...account taking over the SA&AP Ry" -- original 12 functions marked as "Void" on the Statement Showing Levers...
  1926, September 23 SP interlocking plan D-1045 is issued (presumably to document the new cabin interlocker design)
  1927, March 10 "Replaced in service as cabin interlocker"
  1937, June 14 Statement Showing Levers... is "Rewritten"; 1927 instead of 1937 would make more sense given the cabin in-service date; the new Statement Showing... is undated
  1940 interlocker controls relocated to Tower 139
  1941, January 2 "Out of service"

Above: This document obtained from SP by Carl Codney shows numerous revisions over the years as Tower 5 was taken in and out of service, and modified. A newer document, filled out only in handwriting, was created when this one was "Rewritten 6/14 - 37". Given the 5-10-27 date of the cabin interlocker operation, it is possible that "37" should be "27". The new document ("Drawing D-205") merely repeats the function definitions, with one additional handwritten notation: "Out of service Jan. 2 - 1941."

From the SP documents, the tower timeline appears normal until November, 1918 when it was "temporarily" taken out of service for a 16-month period for unknown reasons. After reinstatement, there are no other operational notes until it was removed from service in 1925 when SP acquired the SA&AP. This removal was consistent with the original RCT policy that required numbered interlockers only where two different railroads crossed. Once the SA&AP had been brought formally under T&NO control, the numbered interlocker was, in theory, no longer required or subject to RCT management, even though the interlocking function might still be valuable. This concept had changed over time, however, beginning with Tower 121 where, in April, 1925, SP requested approval for its yard tower in San Antonio even though no other railroads were involved. It is likely that after the removal of Tower 5 from service due to the SA&AP acquisition, SP evaluated local operations and decided that a cabin interlocker was appropriate. It is fair to assume that SP's interlocker plan dated September 23, 1926 was the new cabin design and that it was submitted to RCT for approval. About six months after Tower 5 was "replaced in service as cabin interlocker on March 10, 1927...", Santa Fe's pending approval for Tower 135 in Canyon again raised the specific issue of whether a single-railroad interlocker needed RCT approval. RCT said "Yes."

The 1928 RCT Annual Report was the first to list Tower 5 as an 8-function "mechanical-cabin". Cabin interlockers were used for simple crossings where the traffic was insufficient to justify a manned tower, typically in cases where one line was heavily used and the other lightly used. The interlocker normally would be lined to permit continuous movement on the busier track. When a train approached on the lightly used line, the crew would stop and manually set the interlocker signals to permit passage over the crossing. After crossing, the signals would be re-lined by the train crew to allow trains on the busier line to resume uninterrupted operation. Tower 5 was unusual in that neither line would be considered a main line, hence there may not have been a "busier line". There were other locations in Houston (e.g. Tower 104) where T&NO traffic to or from Englewood Yard could be routed on to, or off of, the former SA&AP line west of Houston. This undoubtedly impacted Tower5's traffic and presumably motivated the downgrade from manned tower to cabin interlocker. RCT files mention that Tower 5's cabin interlocking controls were combined with Tower 139 beginning in 1940, suggesting that a remote control system was installed. SP's document says that the Tower 5 interlocker was "out of service" on January 2, 1941.

Site Photo, Tower 5 foundation (Jim King, December 2006)

Above: This crumbling concrete foundation was found precisely where Tower 5 appears on the Sanborn map. Whether this was the foundation for the tower, or the cabin interlocker, (or both!) is unknown. It seems too small to have been a regularly manned structure, but this may not encompass the entire foundation.

Track Chart, T&NO Clinton Branch (courtesy, T&NO Archives)

Above: This image extracted from a 1926 T&NO track chart of the Clinton Branch shows the T&NO tracks crossing the SA&AP tracks west of Baer Jct., and includes a close-up of this crossing in the upper left corner. Tower 5 is shown located on the southwest corner of the diamond.

Additional Photos, Tower 5 Site, December 2006 (Jim King photos)
Above Left: Tracks to the Tower 5 site remain in place from the east. The grade crossing signals are for Hirsch Rd. Above Right: The tracks from the east curve to the north and then make an S-curve back slightly to the east to connect to the original northbound track alignment. Below Left: To the west, the former T&NO Clinton Branch toward Tower 139 is abandoned. Below Right: The view to the south from the Tower 5 site shows an odd-looking greenbelt occupying the former SA&AP right-of-way toward Buffalo Bayou.

  Left: This 1962 image from historicaerials.com clearly shows a distinct, rectangular shadow denoting some kind of structure located in the southwest quadrant of the Tower 5 site. This is precisely the same location where the tower stood. The height cannot be estimated, so it could be a walk-in hut used as a cabin interlocker, or it could be that the original 2-story tower structure survived into the 1960s (i.e. perhaps the cabin interlocker controls were installed inside the original tower.) The shadow remains visible on 1964 and 1966 lesser quality imagery, but it is clearly missing from 1973 and later imagery. Right: This 2002 image shows that tracks were still present in the southeast quadrant of the site, crossing Clinton Dr. to serve businesses to the south. The tracks stopped a few yards short of Buffalo Bayou.  

Tower 5 Site, Simulated 3-D View (from Google Maps)

Above: Looking south, the only surviving track at Tower 5 is the northeast leg of the junction.

Below: This north-facing "bird's eye view" map of the Tower 5 site from c.2008 shows box cars blocking Hirsch Rd.

Location Map, Tower 5

Last Revised: 2/26/2019 JGK - Contact the Texas Interlocking Towers Page.