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Marquam Bridge

Marquam Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: September 3, 2018

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Key Facts

Facility Carried / Feature Intersected
I-5 Over Willamette River
Portland: Multnomah County, Oregon: United States
Structure Type
Metal Cantilever 14 Panel Multiple-Type-Connected Warren Deck Truss, Fixed and Approach Spans: Metal Stringer (Multi-Beam), Fixed
Construction Date and Builder / Engineer
1966 By Builder/Contractor: American Bridge Company of New York, New York and Engineer/Design: Ivan D. Merchant

Technical Facts

Rehabilitation Date
Main Span Length
440 Feet (134.1 Meters)
Structure Length
5,280 Feet (1609.3 Meters)
Roadway Width
114 Feet (34.75 Meters)
3 Main Span(s)
NBI Number

Historic Significance Rating (HSR)
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Bridge Documentation

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

View Historic American Engineering Record (HAER) Documentation For This Bridge

HAER Data Pages, PDF

View Historic Bridge Inventory Sheet For This Bridge

HAER Documentation, Willamette River Bridges - Data Pages - Drawings -Timeline

This utilitarian mid-20th century truss bridge is noted for its unusual double-deck cantilever truss design. The bridge has a local reputation as the "ugly" bridge, since it lacks the aesthetics of earlier bridges, and even bridges built after this bridge such as the Fremont Bridge were designed with a greater attention to aesthetics (as unusual as that normally is in modern bridge design). Despite this reputation for being "ugly," the bridge is nicer looking than a typical slab of concrete, and it also has some interesting design details. Double-deck bridges are uncommon, and this example with its cantilever truss design is particularly unusual. The design includes a suspended span between the cantilever arms of the center truss span.  It appears this bridge was constructed using rivets to attach part of the truss gusset plates in a shop setting, while the remaining fasteners on the connections which would have been installed in the field were made using bolts. The bridge also includes an enormous and complex series of approach ramps, the design and details being beyond the scope of HistoricBridges.org's documentation. The total length given here is a rough measurement from each end of the approach ramps when traveling over the bridge via I-5, which comes out to about a mile in length. The National Bridge Inventory counts the "bridge" as just the three truss spans, which total 1,044 feet, however these truss spans do not even complete the crossing over the river, with adjacent ramp girder spans crossing the remainder of the river. An exact definition of where this bridge starts and ends is not easy to establish. The bridge has alterations that appear to be earthquake-related retrofits, particularly in the area of the hangers for the suspended span.

The general contractor for this bridge, Kiewit Corporation of Omaha, Nebraska, remains in business today as one of the largest contractors in the country. American Bridge Company was the steel fabricator for the bridge.

This bridge is tagged with the following special condition(s): Double-Deck


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