H&H is an American infrastructure engineering company specializing in the design and management of bridges and other transportation and architecture projects. The firm was founded in 1887 by John Alexander Low Waddell, a structural engineer who pioneered the design of large-scale moveable bridge. Originally incorporated in Kansas City, Missouri as J.A.L. Waddell, Consulting Engineer, the company was renamed throughout the early 20th century as Waddell added junior partners to the organization. In 1920, the firm moved its headquarters to New York City, where it would go on to design many important bridges int the area, such as Newark Bay Bridge (rail), the original Goethals Bridge, and Marine Parkway Bridge.

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.