Adair Viaduct

The Rock Island Railroad provided a vital transportation link for Adair, the county seat of Adair County, as it passed through the town. But heavy rail traffic on this trunk line caused problems, sometimes snarling street traffic and creating a dangerous on-grade crossing. In 1908 the county erected an overpass over the railroad near the spot of a celebrated train robbery by Jesse James. Later the intersection of the Great White Way and the Farmers Highway - two early regional routes designated in 1914 and 1916, respectively - the steel structure carried increasingly heavy traffic in the 1910s. By the early 1920s, it needed replacement. In 1923 the Iowa State Highway Commission (ISHC) designed an immense concrete viaduct for the crossing. "The structure, a three-span arch bridge, is 192 feet long with a twenty-four-foot clear roadway and a five-foot sidewalk," the commission reported in 1924. "It is of the ribbed open-spandrel type of arch. The main span is 80 feet in length and the approach spans are each 56 feet. The approach spans are somewhat unusual for Iowa, being unsymmetrical... The reason for this type of approach span is that the viaduct is located over a deep cut and this type of span fits the typography. The monumental columns on either end and the treatment of the hard [hand) rails leading to the approach spans have been made to harmonize with the landscaping in connection with the city park at the southwest end of the bridge." In May 1923 the Adair County Board of Supervisors awarded a contract to build the Adair Viaduct to the Federal Bridge Company for $42,263.00. The Des Moines contractors began excavating for the concrete substructure soon thereafter; by June 1924 the bridge was opened ceremoniously to traffic, "with the usual accompaniment of music, speeches, and motion pictures," the highway commission reported. After the hubbub of the dedication ceremony died down, the Adair Viaduct functioned as a regionally important railroad overpass. It remains in use today in essentially unaltered conditions. "Jesse James, the notorious train holdup bandit, would hardly recognize the Rock Island crossing [at Adair), should he chance to come upon it today, as the scene of his famous Adair train robbery," the state highway commission reported in June 1924. "Near the top of the steep grade and long curve leading into the town of Adair from the southwest, where this celebrated affair of many years ago took place, there now stands one of the finest examples of rail. road crossing danger elimination by separation of grades and a viaduct in the state of Iowa."

The viaduct provided an important entrance to the town from the south. Jesse James notwithstanding, the true significance of this handsomely proportioned structure is technological and aesthetic. Despite an often-stated preference for concrete for highway bridges, ISHC designed steel trusses for its medium- and long-span structures. As a result, most of Iowa's concrete arches feature relatively short spans and filled spandrel configurations. Less than ten open-spandrel arches have been identified by the state historic bridge inventory, of which the Adair structure is a distinguished example. The viaduct is also noteworthy for its aesthetic handling. ISHC rarely embellished its bridges with any architectural treatment, eschewing aesthetics for functionality. With its decorative guardrails and flanking towers, the Adair Viaduct thus marks a rare foray for the state agency into bridge aesthetics. As a regionally important crossing, and a well-preserved example of an uncommon structural type in Iowa - and a site for local lore - the Adair Viaduct is both historically and technologically significant among the state's highway spans.