The Seventh Street Improvement Arches, carrying East Seventh Street across an abandoned railroad cut on the eastern edge of downtown St. Paul, are a skewed, double-arched, masonry highway bridge constructed according to the helicoidal or spiral method. Buttressed at each end by perpendicular wing walls, the bridge displays two arches surmounted by a well defined coping on top of the parapet. Although the ring stones are cut to simulate the appearance of semicircular right arches, the two vaults are of skewed construction with voussoirs laid in helicoidal or spiral courses. The east arch measures 41 feet in oblique span, with a spring line about 9 feet above grade. The west arch is 11 feet shorter at 30 feet and springs about 12 feet above grade. Originally, the west arch accommodated three railroad tracks, the east arch two tracks. All trackage has been removed. Measuring 124 feet in width, the bridge supports at least 15 feet of earth fill surmounted by a concrete trestle, which, in turn, carries a four-lane black-top roadway and concrete sidewalks bordered by metal railings with concrete balusters. The trestle was constructed when the roadway was widened in 1930. These alterations do not significantly affect the original design.
The bridge features two types of limestone, a locally quarried gray stone that was widely used in 19th century St. Paul for foundation work and a finer-grained, buff-colored stone from Kasota, Minnesota, that was shipped throughout the state for a variety of building purposes. The abutments, pier and wing walls are built of the local material. The voussoirs, ring stones, coping and spandrel walls are of Kasota stone. All stonework is rock-faced, coursed-ashlar masonry with one-half-inch joints. By way of embellishment, intradosal surfaces are bush hammered and ring stones have tooled margins on top and bottom. The center pier also has a rounded, ornamental cutwater.