Year constructed: 1914
Alternate name: North Carolina Avenue Bridge
Bridge type: Concrete Filled Spandrel Arch
National Register of Historic Places status: Listed
Length: 116 feet
Width: 35 feet
Spans: 2
FHWA: 008140
Jurisdiction: City of Mason City
Location: North Carolina Avenue over the Winnebago River in Mason City, Section 3, T96N-R20W (Mason Township)
Details
This concrete filled spandrel arch carries North Carolina Avenue, once known as Stewart Avenue, across the Winnebago River in a residential district in Mason City. Preparation for erecting this structure was well underway by November 1913, the date on plans produced by the Iowa State Highway Commission. For an unknown reason, however, it was not until February 1914 that the city petitioned the county for a new bridge across Lime Creek (now the Winnebago River) on Stewart Avenue. The city promised to raise $1,500 toward the cost of construction if the county would move the existing bowstring arch-truss at that site to another location. The county opened construction bids for the new concrete arch bridge from nine contractors on March 23, 1914. Low bidder at $12,775, N.M. Stark of Des Moines won the contract, which included an additional $125 for removing the old bridge. Stark began work soon thereafter and the bridge was completed later that year. Stark built a number of bridges in Cerro Gordo County during the early 20th century, including another concrete deck arch in Mason City, the State Street Bridge, in 1903. The Stewart Avenue Bridge continue to carry regional traffic in unaltered condition.
From its inception, the state highway commission was a strong proponent of the use of concrete for bridge construction. After ISHC's re-organization in 1913, the agency almost immediately began developing standard designs for small-scale concrete slabs and girders. For larger bridges, such as this structure in Mason City, the highway commission engineered special designs. The Stewart Avenue Bridge is one of several such concrete structures designed by the highway commission in the 1910s in urban and small-town settings. (The period in which ISHC used concrete arches was brief, as the agency turned largely to more efficient structures in the early 1920s.) The use of the concrete arch satisfied both ISHCs penchant for concrete and the agency's desire to incorporate an architectural expression into its city and town bridges. The highway commission was well award of the precedent it was setting with the Mason City structure, featuring a picture of the new Stewart Avenue Bridge and the bowstring it replaced in its annual report for 1913-14. "Treacherous danger in the bow string bridge," the highway commission characterized the older structure in August 1914, "A beautiful concrete arch has just taken its place." With its integral light standards, balustrade railings and wide roadway designed for an interurban rail line, the Stewart Avenue Bridge well represents ISHC urban design of the 1910s [adapted from Hybben, Roise and Fraser 1992].