McCullough began working for the Marsh Bridge Company in Des Moines, Iowa, where he remained for one year.
He then went to work for the Iowa State Highway Commission.
He moved to Oregon in 1916 and became an assistant professor of civil engineering at Oregon Agricultural College, and the sole structural engineering professor at the school.
In 1919 he became the head of the Bridge Division of the Oregon Department of Transportation, making him personally responsible for the design of Oregon's bridges at a time when the state was completing Highway 101.

His designs are well known for their architectural beauty.
McCullough advocated that bridges be built economically, efficiently, and with beauty.
He helped design over 600 bridges, many with architectural details such as Gothic spires, art deco obelisks, and Romanesque arches incorporated into the bridges.
In 1928, he graduated from Willamette University College of Law and passed the bar the same year.
In 1935 he moved to San José, Costa Rica to help design bridges on the Pan-American Highway.
He returned to Oregon in 1937 to become the assistant state highway engineer.
McCullough began working for the Marsh Bridge Company in Des Moines, Iowa, where he remained for one year. He then went to work for the Iowa State Highway Commission. He moved to Oregon in 1916 and became an assistant professor of civil engineering at Oregon Agricultural College, and the sole structural engineering professor at the school. In 1919 he became the head of the Bridge Division of the Oregon Department of Transportation, making him personally responsible for the design of Oregon's bridges at a time when the state was completing Highway 101.
His designs are well known for their architectural beauty. McCullough advocated that bridges be built economically, efficiently, and with beauty. He helped design over 600 bridges, many with architectural details such as Gothic spires, art deco obelisks, and Romanesque arches incorporated into the bridges. In 1928, he graduated from Willamette University College of Law and passed the bar the same year. In 1935 he moved to San José, Costa Rica to help design bridges on the Pan-American Highway. He returned to Oregon in 1937 to become the assistant state highway engineer.
Conde McCullough