On Sunday, I identified this photograph as one taken during the Monster Street Parade that took place on September 9, 1919, as part of the Welcome Home Celebration after World War I. A reader corrected me. The picture does not show the parade that celebrated the return of the soldiers after the Great War; instead it shows a parade that happened around the time the United States entered the war in 1917.
According to my source, what is being rolled down Union Street in this picture is the "Victory Ball," which was rolled all the way from Buffalo to New York City in 1917 to encourage citizens to support U.S. involvement in the war by buying Liberty Bonds. When the ball rolled through cities and villages along the way, it was the occasion for a parade.