Janssen & Spaans Engineering opened its doors in the early 1980s, but founders Hubert Janssen and Leo Spaans had many years of experience with concrete bridge designs before that. The two previously had worked together in the Netherlands for the engineering firm BVN. That company had a long history with prestressed concrete designs, as one of its own founders had been a student of Eugene Freyssinet of France, acknowledged as the inventor of prestressed concrete.

Spaans came to America in 1977 as part of a BVN team that worked with the Indiana-based engineering firm STS. Shortly after, the two companies merged to create BVN-STS, which later was purchased by HDR. Janssen and Spaans broke off on their own a few years later, focusing at first on segmental bridge designs. The company soon expanded its expertise beyond segmental bridges to all types, as well as pavement and roadwork projects.

JSE has created designs for a multitude of bridges, including some highly complex ones that have become its forte. Throughout that history, JSE has found one maxim to be true: Properly designed, a concrete bridge will outlast, outperform, and underbid any alternative.