Rio Puerco Bridge

Serving local traffic as a frontage road for I-40 across the Rio Puerco, the former U.S. 66 bridge across the Rio Puerco is significant for its long association with highway transportation in New Mexico dating to the early 1930s. The longest single-span Parker through truss design bridge in New Mexico, it is also significant for embodying the design, materials, and methods of construction associated with that bridge sub-type.

When federal highways first received a systematic numbering in 1926, many of the roads included in the system in the western states were simply local roads spliced together to create a makeshift network of federal highways. Only in the late 1920s and 1930s did engineers have the resources to plan and construct more efficient, safer alignments. In New Mexico, the original alignment of U.S. 66 used local roads, following a circuitous alignment west of the Rio Grande. In the late 1920s, Albuquerque boosters advocated straightening the alignment, shifting it to run due west from the city. In order to achieve this goal, they succeeded in building a bridge across the Rio Grande at Old Town (1931) but still required a bridge at the Rio Puerco. After several years of lobbying the State Highway Commission, by the early 1930s, they succeeded in their petition to have the so-called Laguna Cutoff placed on the federal road system and, thus, have projects improving the cutoff become eligible for federal matching funds. The Rio Puerco Bridge was included in federal funding in 1933 as part of the Roosevelt Administration's effort to use emergency monies for highway construction. Funded under EFAP-178-A, the bridge was completed within the year, opening the Laguna Cutoff for transcontinental traffic. In 1937, the alignment officially became U.S. 66.

Although the water flow in the Rio Puerco is often minimal, the river is capable of torrential flooding, a fact underscored by its severely eroded floodplain and river banks. In the early decades of the twentieth century prior to efforts at stabilizing degraded rangelands within the river's drainage area, the river posed a major challenge to highway engineers, earning the reputation of being an "outlaw" river capable of "cloudburst" flooding that threatened bridges and roads. In the fall of 1929, the river inflicted its worst damage, washing away several bridges, including the bridge several miles downstream that then served U.S. 66. As a result, engineers determined to construct bridges that would withstand future floods.

The selection of the Parker through truss design at what, four years later, would become the U.S. 66 crossing reflected the highway department's partiality to that design in many of its major projects of the late 1920s and 1930s. In order to compensate for the eroding floodplain and its unstable river banks susceptible to scouring during flooding, engineers designed a bridge employing unusually massive abutments built on deeply driven pilings. They then constructed a single 250-foot span capable of clearing the entire floodplain of the river. The BPR considered the bridge the longest single-span Parker through truss bridge in the Southwest. With its heavy steel members, the bridge appeared especially suited to handle the increasing traffic flow along what was becoming a major east-west highway.

The setting of the bridge over the deep, eroded course of the Rio Puerco conveys a strong feeling of how truss bridges appeared along New Mexican highways prior to World War II. The polygonal upper chords of its superstructure appear in marked relief to the newer twin steel beam bridges of I-40 which parallel it. When the section of the interstate at Rio Puerco was completed in the 1960s, the bridge and the former Route 66 alignment to the east became a part of the frontage road. That road section, including the bridge, treated as an element of the highway property, has been nominated for listing in the National Register of Historic Places as an addition to the multiple property submission, "The Historic and Architectural Resources of Route 66 through New Mexico."