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Gordon Avenue Viaduct


East Approach To Grand Avenue Viaduct Looking West

Photo by Bruce A. Harms, LBA; Summer 1996, for HAER

View photos at Library of Congress

BH Photo #124447


Street View 


Viaducts have long been a part of the urban fabric of Iowa. Beginning as early as the 1880s, the railroads and municipal authorities were concerned about the dangers and bottlenecks created by on-grade, inner-city crossings. Of all the viaducts built by ISHC during this period, none could approach the Grand Avenue Viaduct in Sioux City for scale. Carrying this city street over railroad tracks, other city streets and the Floyd River, this multiple-span steel deck girder structure extends over three-quarters of a mile through the downtown district. The impetus for the viaduct came in 1934, when Congress, in an effort to create jobs during the Depression, passed the Hayden-Cartwright Act allowing federal monies to be used for road and bridge construction within municipalities. Taking advantage of the legislation, the Iowa State Highway Commission began the design work for the Sioux City viaduct in 1935. But rather than design the immense structure in-house, however, ISHC commissioned Kansas City engineers Ash, Howard, Needles and Tammen for the project. AHNT completed the drawings, and the highway commission designated the project WPGM 604, soliciting bids in June 1936 for the viaduct's construction. The following month a contract was awarded to the C.F. Lytle Company of Sioux City for $783,932.01. Construction commenced in July and was completed in November. Extending from Court Street to South College Street, the Grand Avenue Viaduct was comprised of some 54 plate deck girder spans, with a maximum span length of 127 feet and a roadway width of 32 feet, with two 4-foot sidewalks. The structure was huge, consuming almost 13,000 cubic yards of concrete, 1.1 million pounds of reinforcing steel and 6.2 million pounds of structural steel. The bridge, as completed in November 1936, featured ornamental guardrails and 49 light standards. The viaduct carried inner city traffic as well as the traffic of U.S. Highway 75 for 26 years, with only maintenance-related repairs. In 1962, however, three new spans were added to extend the viaduct over the relocated channel of the Floyd River. Then, in 1965 the structure's roadway was increased to its current 56-foot width by adding welded steel girders and extending the existing piers. Removed during this latter alteration were the original lights and rails. Grand Avenue has since been renamed Gordon Avenue, and the viaduct continues to carry heavy traffic through downtown Sioux City. The Grand Avenue Viaduct is distinguished as Iowa's longest grade separation and, indeed, the state's longest bridge other than the Mississippi River structures. Although altered, it is a massive and significant example of highway bridge construction in Iowa in the 1930s [adapted from Fraser 1993].


Steel stringer bridge over Over UPRR, Streets on IA 12/US Business 20 in Sioux City
Sioux City, Woodbury County, Iowa
Open to traffic
Built 1936; rehabilitated 1967
- Ash, Howard, Needles, & Tammen of Kansas City, Missouri
- C.F. Lytle Co. of Sioux City, Iowa
"Extending for over three-quarters of a mile, the Grand Avenue Viaduct is Iowa's longest grade separation and the state's longest bridge except for the Mississippi River structures.

""This document was prepared as part of the Iowa Historic Bridges Recording Project performed durng the Summer of 1995 by the Historic American Engineering Record (HAER). The project was sponsored by the Iowa Department of Transportation (IDOT). Preliminary research on this bridge was performed by Clayton B. Fraser of Fraserdesign, Loveland, CO."

Historian: Richard Vidutis and James Hippen, Summer 1996

Length of largest span: 127.0 ft.
Total length: 3,973.3 ft. (0.8 mi.)
Deck width: 56.1 ft.
Eligible for the National Register of Historic Places
Also called
Formerly called Grand Avenue Viaduct
Approximate latitude, longitude
+42.48925, -96.39064   (decimal degrees)
42°29'21" N, 96°23'26" W   (degrees°minutes'seconds")
Approximate UTM coordinates
14/714444/4707399 (zone/easting/northing)
Quadrangle map:
Sioux City South
Average daily traffic (as of 2017)
Inventory numbers
IA 52830 (Iowa bridge number)
BH 37431 (Bridgehunter.com ID)
Inspection report (as of May 2017)
Overall condition: Fair
Superstructure condition rating: Fair (5 out of 9)
Substructure condition rating: Fair (5 out of 9)
Deck condition rating: Fair (5 out of 9)
Sufficiency rating: 38 (out of 100)
View more at BridgeReports.com

Update Log 

  • February 7, 2014: New Street View added by Luke Harden
  • August 24, 2012: Updated by Luke Harden: Added builder & postcard
  • April 19, 2012: Updated by Luke Harden: Added category "US 20 Business"
  • August 11, 2011: Updated by Luke Harden: Fixed map
  • July 29, 2011: Updated by Luke Harden: Added description and photograph
  • September 14, 2008: Added by J.R. Manning


  • J.R. Manning - thekitchenguy [at] sbcglobal [dot] net
  • HAER IA-87 - Grand Avenue Viaduct, U.S. Highway 20, Business & State Highway 12, Sioux City, Woodbury County, IA
  • Luke