Dr. John Alexander Low Waddell was a Canadian-American civil engineer and prolific bridge designer, with more than a thousand structures to his credit in the United States, Canada, as well as Mexico, Russia, China, Japan, and New Zealand. Waddell’s work set standards for elevated railroad systems and helped develop materials suitable for large span bridges. His most important contribution was the development of the steam-powered high-lift bridge. Waddell was a widely respected writer on bridge design and engineering theory, as well as an advocate for quality in higher education engineering programs. The company he founded in 1887, 'J.A.L. Waddell, Consulting Engineer,' would eventually become the modern day Hardesty & Hanover, a leading moveable bridge engineering firm. Many of Waddell's surviving bridges are now considered historic landmarks.

John Lyle Harrington was an American civil engineer and a leading expert in the field of moveable bridge design. He was a senior partner in several bridge engineering firms, President of the American Society of Mechanical Engineers in 1923-24, and Chief of the engineers' board advising the Reconstruction Finance Corporation.