A structural study examines the oldest remaining metal bridge in the Commonwealth of Virginia, a wrought iron bowstring arch-truss, designed and manufactured by the King Iron Bridge Company. Finite element analysis is used to evaluate interaction between arch and truss, and the results are compared to field measurements from a live load test. The study reveals that diagonal truss elements decrease arch bending by distributing concentrated vertical loads along the arch toward the abutments in a way consistent with that of modern network arch bridges. With truss diagonals absent, vertical bridge deck deflection doubles. Underslung portal frames provide lateral stiffness to the arch, an innovation that accommodated a shallow arch profile conducive to transportation and erection.