Union Square is now renowned for its Greenmarket and the subway station with the prerecorded paternoster:
"Attention all passengers! Please stand clear of the moving platform as trains enter and leave the station. Thank you!"
But in earlier days, it was the focal point for demonstrations and soap-box speeches. It was also the theatrical district, so there were always plenty of crowds to preach to ; the same situation pertains in Times Square today.
As time went on and the crowds increased, being heard over the throng was a considerable challenge. Stepping in to remedy this problem was Allard Ochsenberg, an Alsatian clockmaker, who invented a solution for this: the pay megaphone! You'd put a penny in and get 15 minutes of megaphone use before a felt shutter deep in the device would cut you off. The megaphones were made of cast iron, mounted on gimbals so the voice could be directed at passing shoppers. Similar devices, with binoculars, are used for sightseeing to this day!
A battery of eight of these megaphones were installed on the west side of Union Square, where today used books are sold. When all stations were occupied, the peculiar acoustic properties of the devices made it seem like tuning through a dense patch of talk-radio programs!
The pay megaphones were removed during the Second World War and symbolically sold as scrap.