The Split Rock Bridge is historically significant as an outstanding example of an ornamental park bridge, achieving its aesthetic effect through the purity of its form and the beauty of its random-ashlar masonry. In addition, the bridge displays the largest stone-arch span of any active highway bridge in the state. Split Rock Bridge. The bridge survives in unaltered condition.
In 1935, state and federal officials authorized the construction of a masonry dam across Split Rock Creek in the southwest corner of Pipestone County. The project had both short- and long-term goals. It aimed at providing immediate employment for the local citizenry, as well as future recreational opportunities for the entire region. By impounding the waters of Split Rock Creek, the dam created the county's only lake, intended as the nucleus of a small state park known as Split Rock Creek State Recreational Reserve. The general plan also included the construction of a stone-arch highway bridge on the park's access road, just downstream from the dam. Although funded as separate projects, the bridge and dam seem to have been conceived as an integrated landscape design. Rising above the surrounding prairies, the two massive masonry structures form a visually arresting point-and-counterpoint of delicately colored pink Sioux Quartzite.
In December, 1936, as the dam was nearing completion, the WPA submitted final specifications for the stone-arch bridge to the Minnesota State Highway Department. The specifications and presumably the plans were prepared by Elmer Keeler, the Pipestone County Highway Engineer, and Albert G. Plagens, a consulting architect from New Ulm, Minnesota. Plagens is best known for his work on another New Deal project, the WPA-sponsored, Moderne-style Public Library and Historical Museum in New Ulm. Construction on the bridge commenced in 1937 using Sioux Quartzite quarried a few miles away near the city of Jasper, long-known for its building stone and accomplished masons. The bridge was completed in 1938 for an approximate cost of $46,000.
Split Rock Bridge was clearly intended to showcase the area's masonry tradition. On most New Deal bridge projects in Minnesota, stonework was used only as a decorative facing. In contrast, the Split Rock Bridge is an authentic, load-bearing stone arch with an impressive 50-foot span. Instead of the Moderne or historic revival styles customarily employed during the period, the bridge has an almost modernist simplicity, which focuses attention on the natural colors and textures of the local Sioux Quartzite, skillfully laid in a captivating random-ashlar pattern.