The CQA Four Mile Bridge spans the Big Horn River in Hot Springs County, Wyoming. The bridge was erected in 1927-28 by the Charles M. Smith Company and spans with a total length of . The rigid 7-panel Pennsylvania through-truss was nominated for inclusion on the National Register of Historic Places as one of forty bridges throughout Wyoming that collectively illustrate steel truss construction, a technique of bridge design that has become obsolete since the mid-twentieth century. The bridge rests on concrete piers and abutments and is approached by two Warren pony trusses.
The Four Mile Bridge was placed on the National Register of Historic Places in 1985.