One of the first highway bridges over the Missouri River, the Old Trails National Highway Bridge was a significant link in Missouri's transportation system for nearly 75 years. In 1921, Boonville residents Thomas A. Johnston and John Cosgrove led a local effort to construct the bridge and formed the Old Trails Bridge Company, which raised money by selling stock. Construction began in March 1922, and in October 1922 the company transferred the project to the Missouri State Highway Commission, which secured federal funds and oversaw completion. Cooper and Howard counties both passed bond issues to help finance the work. The bridge consisted of three Pennsylvania through truss spans, each 420 feet long, and three Parker through truss spans, each 280 feet long, with seven large concrete piers supporting the main steel spans. Ten spans on the south approach, nine of concrete and one of steel, were supported by concrete column bents. The structure measured 2,666 feet in length, more than one-half mile. Taking more than two years to complete, it was dedicated by Missouri Governor Arthur Hyde on July 4, 1924, at a total cost of over $563,000; one worker was killed during construction. The bridge became an important connection on U.S. Route 40 between Kansas City and St. Louis and on Missouri Route 5 connecting the borders of Iowa and Arkansas. In 1938 a pedestrian walkway was added along the east side, and the original timber floor was replaced with a steel grating deck that proved unpopular with motorists because it made steering difficult and dangerous. Harrington, Howard and Ash designed the bridge and supervised construction; the Missouri Valley Bridge and Iron Company built the seven concrete river piers, the Mount Vernon Bridge Company erected the six steel truss spans, and W. J. Cochran and Son of Boonville built the ten south approach spans and laid the original yellow pine timber deck. The construction of a new bridge in 1997-98 ended its era, and the old bridge was demolished in the summer of 1998.
