The State of Ohio has 139 inventoried masonry arch bridges and many more culverts, in road and highway service. Many of these structures have been identified as historically significant, making their replacement difficult, and their load-rating and rehabilitation imperative. In this study a procedure for load rating masonry arch bridges is developed. The procedure follows the practice of the AASHTO Manual for the Maintenance Inspection of Bridges, Load Factor Method. The geometry of the structure is determined by field measurement, and appropriate material properties are determined by inspection or testing. A unit width of the structure is analyzed using commercially available place frame analysis software. The moments and axial forces in the arch ring under combinations of load and rating factors are compared to estimates of the capacity of the masonry to determine inventory and operating ratings. Field tests of seven structures under various configurations of truck loading have been used to validate the analytical model. The proposed analysis and rating procedure is applied to the structures in this study.