The Department issued this 3-cent stamp to commemorate the centennial anniversary of the Soo Locks through the Sault Sainte Marie, Michigan, post office on June 28, 1955, the opening day of the Soo Locks Centennial Exposition.
The overall design of the stamp is a map of the Great Lakes against a scenic background composed of sky, water, and a lake steamer under way. Each lake carries its name in a dark, modified Roman. Though enlarged in proportion to the map area, a steamer afloat in the Soo Locks appears in the general location of the locks. The denomination "3c" in dark Gothic appears in the upper left corner. Arranged in three lines and located in the upper right portion of the stamp is the wording "Soo Locks 1855 Sault Sainte Marie 1955." In the upper right corner is the lettering "US" arranged horizontally with the word "Postage," arranged vertically, immediately below. Arranged in two lines at the bottom of the stamp appears, "A Century of (in whiteface Gothic) Great Lakes Transportation (in dark, modified Gothic)."
The stamp was printed by the rotary process, electric-eye perforated, and issued in panes of fifty stamps each. The printing of 110 million stamps was authorized.
Postal Bulletin (June 7, 1955)