The Caveman Bridge is probably Grants Pass' most visible and recognizable landmark in the city. Built in 1931 by renowned engineer Conde B. McCullough this bridge still functions in the same capacity it did in 1931 and appears to be able to function as a bridge for another 100 years.
The following information is taken from Bridgehunter.com to highlight McCullough's background:
Conde Balcom McCullough (1887-1946) was the notable State Bridge Engineer for the Oregon State Highway Department from 1919 to 1935. During McCullough’s tenure as bridge engineer, Oregon developed one of the most impressive collections of beautiful and efficient bridge in the United States.
McCullough began his career designing bridges under another notable engineer, James B. Marsh and his Marsh Engineering Company. After a year working for Marsh, McCullough joined the Iowa State Highway Commission where he developed bridge design standards and assisted in designing bridge throughout Iowa. During this time McCullough served as an expert witness during patent infringement lawsuits between Daniel Luten and Marsh.
McCullough was appointed the Oregon State Bridge Engineer in 1919 after a short stint at Oregon Agricultural College as a professor. As the State Bridge Engineer for the Oregon State Highway Department, McCullough brought forth a three part philosophy to bridge design. His three major points were to make the structure fit the site in which it was being built, have the bridge be cost effective, and finally he emphasized building structures that were pleasing to the eye.
McCullough is most widely known for his work with reinforced concrete arch bridges. McCullough assisted in pioneering different design and construction methods in concrete arch construction, along with writing text books on the subject of concrete arch design. Some of his most notable reinforced concrete arch bridges include the Rogue River Bridge in Gold Beach and the Winchester Bridge in Roseburg.
McCullough’s most recognizable accomplishment was managing the design and construction of the bridges on the Oregon Coast Highway. Over the course of two years McCullough’s staff completed the design and construction of five major coastal crossing all measuring between 1600 to 5400 feet in length. The bridges were designed with many of the architectural details that have made McCullough’s bridge some of the most beautiful in the world.
After the completion of the coastal bridges McCullough left Oregon to design bridges on the Pan-American Highway in Central America for the Bureau of Public Roads. McCullough gave up his position as state bridge engineer but upon his return he served Oregon as the Assistant Highway Engineer until is untimely death in 1946.
The legacy McCullough left still lives in the design and maintenance of Oregon Bridges. Oregon is one of the leaders in historic bridge preservation along with creating innovative and eye pleasing structures to replace aging structures of McCullough's era. In 1947 the longest of McCullough’s coastal bridges, the Coos Bay Bridge in North Bend was dedicated the Conde McCullough Memorial Bridge in honor of McCullough.
I found an even more interesting read on McCullough that also includes some old postcard pictures of this bridge when it was new and it can be read in detail here.