State Highway 53 Bridge at the Leon River

The State Highway 53 Bridge at the Leon River was built from 1938 to 1939. This custom-designed Parker through truss bridge with special decorative features is significant for embodying the defining characteristics of a highway department-designed Parker truss bridge.

The Leon River bridge was built on a 7-mile segment of highway which ran between Belton and Temple. Two routes shared this segment, which traversed Central Texas. The east-west route held the shared designation SH 53/US 190. This regional route began at the junction of US 77 in the southern tip of Falls County and extended west through Belton and Killeen in Bell County to Lampasas, the Lampasas County seat. The north-south route, originally known as the Meridian Highway, was designated SH 2 in 1917 when THD selected the first 25 state highways. The route had been redesignated US 81 by the time the bridge was constructed. This route linked Burkburnett and Wichita Falls in North Central Texas with Laredo on the Texas-Mexico border, passing through Fort Worth, Waco, Temple, Belton, Austin and San Antonio.

THD constructed the Leon River bridge to replace the previous bridge, built by the county in 1907, which consisted of one 175-foot truss span with a pony truss span at each end. THD inherited this bridge when the route was designated a state highway in 1917. As was often the practice in pre-highway department bridge construction, the old bridge crossed the river at nearly a right angle. This alignment allowed for the shortest possible bridge length, but also required sharp curves at each end of the bridge, up to 32 degrees in this case. In addition, the bridge had only a 17-foot roadway and a maximum load capacity of 10 tons. For these reasons, the bridge was considered unsafe to carry the amount and type of traffic at speeds commonly traveled in the 1930s. The 1907 bridge, built for horse and buggy traffic, had become functionally obsolete.

As described in a memorandum dated August 3, 1936, THD implemented a temporary measure to rehabilitate the old bridge in 1933: "In December 1933, the structure was completely overhauled under a Maintenance Contract, this work consisting of replacing the floor system with treated timber stringers and laminated floor and tightening several loose tension members of the trusses." As is recounted in the memorandum, the work was not enough to solve the bridge's inherent deficiencies: "Since the repair work was done both pony trusses have been wrecked due to collision by trucks. The pony trusses have been dismantled and the approach spans are now supported by timber pile bents."

In 1936 THD engineers began preparing the plans for the replacement bridge. Consideration was given to applying to the Bureau of Public Roads (BPR) for federal funding, but as described in a memorandum dated June 17, 1937, the eventual relocation of SH 2 (later SH 53), complicated the issue:

It is quite possible that Regular Federal Aid could be applied to the proposed bridge, however, such a procedure would require the submission of the usual route sketch map to the Bureau of Public Roads with a request for Federal inspection and approval of the proposed location. Since the proposed future routing of Highway 2 between and adjacent to the towns of Belton and Temple represent (sic) a rather major departure from the present road and the application of Regular Federal Aid funds on the proposed Leon River bridge may complicate matters should it be desired to proceed with improvements along the proposed future routing of Highway No. 2 within the near future and request Federal participation on proposed construction.

Rather than use a standard design, THD bridge engineers specially designed the 200-foot riveted Parker through truss span for use on the replacement bridge. Nine other Parker truss bridges specially designed by THD survive today. One of these, in Travis County, uses a similar design for its single truss span. As part of an effort to improve the aesthetics of bridge design, particularly for structures in or near urban areas, several decorative elements were incorporated into the design of the Leon River bridge. The bridge substructure, which was readily visible from the Riverside Swimming Pool (now Summer Fun, USA) to the northwest, exhibits arched concrete bents and concrete piers with beveled copings. In addition, decorative steel railing flanks a 5-foot wide pedestrian walkway. The posts are made up of H-beams placed vertically, then cut, bent, and welded to form the curved top end of the post. The top handrail consists of 3-inch piping. Below, two rows of channels between the posts face down. Small square steel pickets of varying lengths hang from the pipe handrail to fill out the railing. These pickets run through holes in the three rows of steel channels and are welded in place. The result is an elaborate and labor-intensive decorative steel railing. This is the most decorative type of steel railing used on THD bridges. The Leon River bridge is one of only three surviving THD truss bridges exhibiting a pedestrian walkway with this type of decorative steel picket railing.

The Texas Highway Commission held bidding for the Leon River bridge in July 1938. After reviewing the three bids received, the commission awarded the project to the low bidder, the Austin Bridge Company of Dallas. Its bid of $93,763 was the only one of the three bids to come in below the THD's estimate of $103,900. The Mosher Steel Company of Houston, formerly Houston Structural Steel Company, owned by the Mosher Steel & Machinery Company of Dallas, fabricated the steel truss span and the pedestrian railing.
The contract executed between THD and the Austin Bridge Company provided for the continued use of the old bridge during construction and for its dismantling upon the completion of the new bridge. In order to accommodate the construction of the new bridge, the old bridge's west end was shifted 8 feet south. THD's efforts to maintain traffic flow over the bridge is reflected in a memorandum to the division (now district) engineer written on February 7, 1939, by the resident engineer:

The Superintendent on the above project has requested permission to place a construction joint on abutment No. 2 in the columns at the intersection with the haunches under the caps. By doing this he can delay the shifting of the old structure with its inconvenience to the traveling public for several weeks, as the backfill can be practically all constructed, and the embankment constructed to the elevation of the old bridge. Incidentally, this will allow us to pass machinery between the columns for compaction of the front slope.

Construction of the bridge began on September 12, 1938, and was supervised by the THD resident engineer in Belton. The THD division engineer and assistant division engineer in Waco joined the resident engineer for monthly inspections of the work. During the construction of the bridge, the THD resident engineer submitted a field change to use "Dardalet rivet bolts" rather than field rivets on the steel member supporting the sidewalk. The Dardelet bolt or interference body bolt, which replaced rivets in steel construction, was a tight-fitting bolt that was nailed into a steel member and set in place with a nut. Because the concrete forming the bridge's sidewalk slab had recently been placed, the resident engineer feared that the riveting operation might cause some cracking of the slab. The bridge was completed on May 31, 1939, at a cost of just over $98,000.

In October of the same year, construction began on a roadside park (since abandoned) located to the northeast of the bridge. In the early 1950s, THD began improving SH 81 and by 1959 the route had been upgraded and designated Interstate 35 (I-35). The original route was relocated as necessary in order to obtain an improved alignment. Most of the segment of highway between Belton and Temple, also used by the SH 53/US 190 route, was shifted 12-mile to the southeast. The original roadway, including the bridge over the Leon River, was retained to serve local traffic as FM 817. This configuration lightened the traffic burden on the bridge, allowing for its preservation in place.