State Highway 3-A Bridge at Cibolo Creek

The State Highway 3-A Bridge at Cibolo Creek, constructed from 1932 to 1933, is significant for embodying the defining characteristics of a THD truss bridge. As such, it meets National Register Criterion C in the area of Engineering at a state Level of significance.

The Cibolo Creek bridge was built on SH 3-A (now I-10/US 90), a branch of the Southern National Highway, SH 3. The Southern National Highway linked Del Rio, San Antonio, Houston, Beaumont and Orange, as well as smaller towns along the route. In the early 1920s, work began on upgrading the segment between Seguin, in Guadalupe County, and Waelder, in eastern Gonzales County. The improved segment was built on new location south of and parallel to the original route. For several years, both branches were in use, with the newly constructed segment designated SH 3-A. By the early 1930s, construction was under way on the extension of SH 3-A from Seguin to San Antonio. The Cibolo Creek bridge and other drainage structures were built on this section of new roadway. Eventually the SH 3-A branch, extending from San Antonio to Waelder, became the primary route and was designated SH 3. By about 1930, the route held the shared designation SH 3/US 90, and by 1938 the SH 3 designation had been dropped.

The Cibolo Creek bridge was built as part of a larger THD project to construct SH 3-A between San Antonio and Seguin. In addition to the construction of the truss bridge, the project included new roadway grading and concrete drainage structures. THD prepared the plans and, because it was a federal aid project, the Bureau of Public Roads (BPR) reviewed and approved them. The THD resident engineer in Seguin supervised the construction of the bridge, which engineers from both THD and BPR inspected.

THD bridge engineers chose the T24-120 design for the truss span of the Cibolo Creek bridge. The T24-120 is one of 25 different THD standard designs the Bridge Division developed for Parker through truss spans; only 11 of these designs are represented by bridges today. The T24-120 was first designed about 1926: a second version was completed about 1932. The Cibolo Creek bridge is the only surviving example of the first version of the T24-120; two bridges conforming to the second version survive in Texas. THD engineers designed the approach spans with exterior I-beams encased in concrete, presumably for an improved appearance.

On May 26, 1932, the Texas Highway Commission opened bids for the construction of the Cibolo Creek bridge and a concrete structure over Salado Creek. The contract for roadway construction and smaller drainage structures had been awarded on December 1, 1931, and construction on this part of the project was already well under way. After reviewing the 18 bids submitted for the bridge construction, the commission awarded the contract to the D.F. Jones Construction Company of Little Rock, Arkansas, which submitted the low bid of $100,614. The Houston Structural Steel Company, owned and operated by the Mosher Steel & Machinery Company of Dallas, fabricated the steel superstructure. Work on the Cibolo Creek bridge and the concrete structure over Salado Creek began on July 6, 1932, and was completed by March 1933. The total cost of the structures came to roughly $100,000, half of which federal funds covered.

In the early 1960s, THD responded to increasing traffic volumes on I-10 by constructing two continuous I-beam bridges adjacent to the Cibolo Creek bridge, retaining the truss bridge on what became the eastbound frontage road. This configuration lightened the traffic burden on the truss bridge, allowing for its preservation in place. Although the construction of the new structures has altered the setting of the truss bridge, as transportation facilities they are compatible with the use of the original bridge and therefore do not significantly compromise its integrity.