An honor for the Balch Gulch Bridge

The 400-foot-long span is added to National Register of Historic Places

Built in 1905, the bridge has gone through three major renovations.

A 400-foot-long bridge that many Portlanders use without giving a second thought has been added to the National Register of Historic Places based on its importance in the city’s development and its vintage construction method.

The Balch Gulch Bridge, completed in 1905, carries Northwest Thurman Street across the gulch between Northwest 29^th and 31^st Avenues. Soon after its completion, the bridge became a popular and well-publicized viewpoint of the young city during the 1905 Lewis & Clark Exposition.

“The city promoted the streetcar route into Willamette Heights as a scenic outing for fairgoers, and vantage points accessible only via the bridge were featured in promotional photographs of the fairgrounds,” historian Michael Taylor wrote in a comprehensive National Register document. “The bridge’s role in showcasing Portland’s natural beauty and development potential helped elevate the city’s image and encourage private investment, while the improved access to Willamette Heights accelerated the neighborhood’s first and most intensive phase of residential growth.”

A wooden predecessor built in 1892 was not strong enough to carry street cars. Until the new bridge opened, trolley riders had to get off a streetcar, walk across the wooden bridge and board another car on the opposing side. Streetcar tracks were removed in 1950.

The 1905 bridge is composed of two trusses of 160 feet and 60 feet in length, sitting on three steel towers atop concrete bases. The deck of the bridge sits on top of the triangular truss structures.

Unlike modern bridge construction, the trusses were held together by pins – essentially large threaded bolts. The pin system allowed for speedy erection and for some modest joint movement, based on load stresses. As historian Taylor notes, pins in newer construction have been replaced by rivets that are considered stronger and less susceptible to wear.

Taylor wrote that pin construction “reflects the dominant connection method for truss bridges erected in the late 19th and very early 20th centuries. By the early 1910s, most new bridges employed riveted joints, and over time Oregon’s inventory of pin-connected bridges has declined.”

The Balch Gulch Bridge underwent renovations in the 1920s, the 1950s and again in 2014. The 2014 work paid close attention to keeping or restoring original visual elements of the bridge, including reconstruction of decorative railings on the sides to match the originals removed in 1955. The 2014 work also added new steel planks as the decking material.

“Despite these alterations, the bridge maintains nearly all its character-defining features, including its Pratt deck truss design, pin connections, original steel trusses and towers with concrete footings, and location spanning Balch Gulch in Northwest Portland’s Willamette Heights Addition,” Taylor wrote. “It therefore retains integrity.”

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