Wing-walking displays were frequently a part of barnstorming displays and air shows in the 1920s, and the Curtis JN-4 "Jenny," was a prime workhorse of the post WW1 barnstorming and air show circuits. The Jenny cruised at 40 to 60 miles per hour, allowing the wing-walkers to stand on the wing despite the air flow, although the performers were billed as death-defying dare-devils..
The image is a postcard image taken in 1925 by an unidentified photographer. The wing walkers were reportedly only miming a tennis match on the upper wing of the plane. The picture shows Ivan Unger (foreground) and Gladys Roy, who were well-known members of the "13 Black Cats" wing-walkers in the 1920s.
Roy customarily wore her high-laced boots while showing her dare-devil specialties of wing-walking and parachuting. She was killed in 1927, at the age of 25, when she apparently distractedly walked into the spinning propeller of a plane on the ground. From Minneapolis, one of her brothers was a pilot and two other brothers also worked in aviation.