A bypass for US-51 was built between the two cities of Peru and La Salle in 1958. That bypass took the name US-51, so the Shippingsport Bridge alignment was called Business-51. The new US-51 bypass crossed the Illinois Waterway with a large steel truss structure about a mile west of the Shippingsport Bridge. Using the new bridge, thru traffic could avoid the city streets of La Salle and avoid waiting in line when the lift span of the Shippingsport Bridge was open.
Interstate highway I-39 was extended south in 1987. It passed to the east of both Peru and La Salle, about a mile upstream of the Shippingsport Bridge. I-39 rejoined US-51 about 2 miles south of the Illinois River. When this new section of I-39 opened, the designation US-51 was moved to the new I-39 highway. The old US-51 bypass was turned back to the state of Illinois, which gave it the name IL-251. Business-51 was retired at the same time, so the highway that includes the Shippingsport Bridge was given the designation IL-351.
Major work was completed on the IL-251 bridge in 1992. The deck was removed and replaced, bearings were repaired, and the pins that held key beams together were replaced.