Conde B. McCullough Memorial Bridge: Engineering as art

In the 1930s, the Great Depression hit the nation hard, and Coos County, Oregon, wasn’t immune to the effects. During that decade, the State Highway Department used state and federal funds to build bridges over the Oregon Coast’s major rivers and bays. The Conde B. McCullough Memorial Bridge was completed over Coos Bay in 1936 at a cost of $2,094,000. This new span, the sixth largest in the world at the time and the longest in the Pacific Northwest, eliminated ferry traffic on the bay between North Bend and Glasgow.

Conde B. McCullough, the bridge’s engineer and designer, combined the Art Deco, Gothic, and Moderne styles into the design elements. From the side, the bridge resembles a giant green spider web supported by concrete stilts. Driving over the span provides another perspective, where the bridge’s arches and cathedral-style spires add a majestic flavor to the panoramic view of sand dunes, sea-washed boulders, and wind-swept evergreens.

The McCullough Bridge was one of the greatest engineering feats ever attempted along Highway 101, which stretches the Pacific Coast from Canada to Mexico. Before construction started, engineers considered many factors essential to creating a safe, usable transportation link and incorporated information from a variety of sciences—meteorology, mining, and mineralogy, among others—into their plans.

Engineers needed to know the depth of bedrock in Coos Bay to determine where to place a foundation slab. Because the bridge had to be built high enough to allow oceangoing ships to pass underneath, engineers needed to calculate the minimum clearance. They had to know the amount of expansion to be expected from structural steel. They also needed to know which type of concrete best resists the action of saltwater and how to protect construction employees, as well as the bridge, against high winds.

During the two-year project, the mile-long bridge consumed a huge amount of materials:

  • 185,000 linear feet of foundation piling
  • 48,000 cubic yards of concrete
  • 62,500 cubic yards of sand and gravel
  • 3 million pounds of reinforcing steel in concrete
  • 5 million pounds of structural steel
  • 5 million board feet of timber

The largest single steel pieces set in place on the bridge, the four main towers, weigh 34 tons.

An average of 250 men worked 30 hours per week, for a weekly payroll of about $7,000. During the week of July 27, 1935, 650 employees were on the job—the all-time high for the project.

To keep the bridge in place in case of high winds, it was fitted with “wind anchor shoes.” Roller bearings allow the steel span to move a few inches back and forth with temperature changes. These wind shoes sit on top of the concrete pillars and penetrate the steel above, allowing the bridge to slide back and forth but not side to side. The resistance on each shoe is 108,000 pounds. All trees on the bay would be blown away before the bridge would even groan.

To set the foundations of the bridge, workers built great cofferdams of timber and steel to hold the water away from the concrete. These cofferdams had to be strong; at a depth of 50 feet, water exerts a pressure of over one and one-half tons against every square foot.

Rain, nature’s most unpredictable asset to Coos, caused many delays on the project. Wet steel means slippery steel. Dozens of days were lost by the men who raised the huge trusses of structural steel into place.

Wet steel can’t be pained, either, so a painting job would have taken a few weeks in perfect weather stretched to approximately 10 months. Rain postponed the laying of the steel to be painted, as well as the painting itself.

Rain also delayed the pouring of flat surfaces that couldn’t be covered with waterproof canvas. If these had been poured, the rain would have washed out cement and weakened the surfaces before they had time to dry and cure.

High winds were always a concern and sometimes displayed their power in humorous ways. Once when a huge crane on the north trestle was being moved, a gust of wind snatched it away from the work crew and blew it at 20 miles per hour toward a waiting truck. The crane stopped a few feet before it reached the truck, well ahead of its pursuers, who could only watch with open mouths and scratch their heads in wonder.

Obviously with all the dangers involved in building the bridge, it’s easy to imagine many casualties during the project, but only two men lost their lives.

As the bridge neared completion, the media started plotting auto coastal tours and publishing detailed accounts of the construction process. The Coos Bay Times planned a trip of the entire length of the Oregon Coast for its readers. Sunset magazine planned one from San Francisco to Portland via Astoria. An issue of Oregon Motorist devoted practically all of its 30 pages toward the bridge’s construction and completion, with articles by McCullough; R.H. Baldock, state highway engineer; and Warren D. Smith of the Department of Geology at the University of Washington.

Of all of the promotions, the most spectacular was a four-color, 24-page publication by Greyhound Bus Lines entitled, “See California and All the West.” A cartoon of two tourists gazing in amazement at the size of the bridge graced the front cover.

After the bridge was completed, the communities of North Bend and Marshfield (now the city of Coos Bay) held a dedication celebration June 5-7, 1936. Plaques with the bridge’s name, then simply Coos Bay Bridge, along with the U.S. Public Works Administration’s construction number, 962, were placed on each end of the bridge. Later, the name was changed to the Conde B. McCullough Memorial Bridge in honor of the designer. The bridge was added to the National Register of Historic Places in 2005.

Today, the bridge still stands in testimony of the insightful engineers and hard-working construction crews who made a vital transportation link along Highway 101. Thousands of tourists and residents cross it annually and appreciate the beauty it adds to the Oregon Coast.

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