Missouri Mule

A photo for the theme of what on earth is going on? in the Vintage Photos Theme Park.

This photo shows nine or more people who are riding in a open vehicle that's popping a wheelie (see a cropped version for a better view of the contraption). Painted on a wall in the background are the words "Missouri [Mu]le." What in the world is happening here?

After some searching, I learned that the Missouri Mule, "known for its strength, hardiness, intelligence and even temper," is the state animal of Missouri. In addition, I found an Ultimate Rollercoaster article about Harry G. Traver, a roller coaster designer and founder of the Traver Engineering Company, who created the "Missouri Mule," an amusement park ride also known as "Bumping Autos." Could this be a picture of the Missouri Mule ride?