100th Street Bridge

• Years constructed: 1957
• Bridge type: Concrete Continuous Box Beam or Girder-Multi
• National Register of Historic Places status: Eligible
• Length: 282 feet
• Width: 28.2 feet
• Spans: 3
• FHWA: 029080
• Jurisdiction: Humboldt County
• Location: 100th Street over the East Branch of the Des Moines River on the Humboldt/Kossuth Line, Section 1, T93N-R29W & Section 36, T94N-R29W (Delana Township)

Details

The 100th Street Bridge is eligible for inclusion in the NRHP under Criterion C as it does meet registration requirements outlined in the MPD as a large continuous box beam bridge of an exceptional span length. The registration requirements include box beam spans of over 100' in length as exceptional. With a main span of 109', this bridge does meet that requirement. The 100th Street Bridge does not meet any other registration requirements and is therefore not eligible under any criteria.

The application of the principles of continuity were applied to later forms of concrete spans including Continuous Box Girders (Type 205) by the mid-1940s. Continuous construction and cast-in-place concrete were a natural marriage for long bridges made of numerous repetitive short-to-medium spans, as well as approaches and viaducts. The short sections of longitudinal steel reinforcement needed only to be overlapped and "tied" together to function as a single continuous structural element once the concrete hardened around it. The "work" to reap the advantages of the continuous concrete bridge was in the design rather than in the construction so state highway departments were quick to adopt the continuous beam and girder bridge forms for a multitude of applications. The labor, materials and equipment required to build simple-span concrete bridges was the same for continuous bridges.