Here’s a moment in time from which one could build a book.
In 1938, a preview parade for the New York World’s Fair with its corporate modernist ethos wound its way through the city. The parade was ten miles long and it included cars from every state in the union.
At the intersection of Thirteenth Street and Seventh Avenue it was cut off by a 50,000-100,000 strong parade celebrating May Day.
One couldn’t script a better symbolic scene.
No disturbances or altercations were reported.
Sources: Robert Rydell mentions the incident in World of Fairs: The Century of Progress Expositions. He cites a 1938 NY TImes article, “Divided Leftists in Quiet May Day,” and “Red Light for May Day March” in World-Telegram.