Walnut Canyon Bridge marks 100 years

Becoming a state had a big impact on Arizona’s roads. Once statehood was achieved in 1912, many infrastructure projects were pursued, like the Walnut Canyon Bridge in northern Arizona.

The Walnut Canyon Bridge lies on the old Flagstaff-Winslow Highway near the small community of Winona, which sits about 15 miles east of downtown Flagstaff. That road later became part of US Route 66.

Plans for construction were completed in 1922 and the bridge opened to traffic in June 1924. Though it’s no longer open to cars, the Walnut Canyon Bridge has been standing for 100 years.

According to the National Park Service, which listed this bridge on the National Register of Historic Places in 1988, the bridge was built with federal dollars:

"After Arizona became a State in 1912, roads advocates began lobbying for assistance to upgrade Arizona’s roads. Individual counties had the primary responsibility for road building and maintenance in Arizona during the 1910s, and county governments were unable to meet the public demand for roads. 

"In 1916, the Federal Government began distributing Federal money to State highway departments. Arizona received $3.7 million for the initial five-year program. In response, the existing State Engineer’s Office became the Arizona Highway Department, which quickly became the State’s largest agency."

The Walnut Canyon Bridge “used a standard 100-foot-long, steel Parker web configuration, with built-up box beams for the upper chords and batten-plated angles for the lower.” The National Park Service offers more details about the bridge:

"[The bridge] has a single span of 101 feet and a 19-foot-wide roadbed. The superstructure is of riveted steel and uses a five-panel Parker through truss. Truss bridges have a combination of members, usually arranged in a triangular configuration, to form a rigid framework. A Parker truss includes an additional element: an upper polygonal chord. The substructure has concrete abutments and wing walls. The floor is a concrete deck over steel stringers. The bridge has steel lattice guardrails with concrete curbs."

Today, the Walnut Canyon Bridge is closed to traffic, but remains in its original condition.

The Walnut Canyon Bridge was an important early part of US 66, the famous east-west transcontinental route across northern Arizona. It also stands as one of just four Parker trusses in ADOT’s historic-bridge inventory.