The iconic design, introduced in the 1930s, features a stop sign that rotates 90 degrees to face street traffic when activated. Once common across the Midwest, Griswolds were widely used by the Minneapolis & St. Louis; Minneapolis, Northfield & Southern; Milwaukee Road; Northern Pacific; and Soo Line among others. A handful with rotating banners remained in operational service into the 2010s, with other holdouts in Hibbing, Minn., on BNSF, and San Jose, Calif., on Union Pacific.
While the charm of the mechanical banner can no longer be found in the wild, there are still half a dozen Griswolds along active rail lines in Minnesota. A list of these signals is available online.