'3M' Mile Marker on Ocean Parkway

Just south of Avenue P on the west side of Brooklyn's Ocean Parkway, a small, one-foot-tall granite rectangle juts out of the ground with a mysterious "3M" carved into its traffic-facing side.

This inconspicuous stone was once a mile marker on Ocean Parkway, a street inspired by the grand boulevards of Paris and Berlin, built between 1874 and 1880 in the middle of Brooklyn, New York.

Originally, Ocean Parkway was a shortcut for pedestrian and horse traffic, as well as strollers and carriages, to Coney Island Beach from Prospect Park. When the parkway was first built, bicycles still had yet to be invented. This mile marker was one of 11 placed every half mile from Prospect Park Circle to the end of Ocean Parkway in Coney Island.

According to the Brooklyn Park Commission, which managed the parkway, it is likely that they were erected around 1876. But over the decades, by 2000, all but the three-mile marker by Avenue P and the five-mile marker on Neptune Avenue had been removed. The five-mile stone was subsequently removed around 2010 when a bus shelter was installed. Today, only the three-mile marker remains. 

Mile markers were a common way to mark private roads from colonial times until the early 20th century. They told the coaches and riders how many miles they had covered and how much further they had to go. Several roads in the city had similar passing signs: the old Bloomingdale Road (now Broadway) in Upper Manhattan, as well as Jackson Avenue (now Northern Boulevard) in Queens, Kings Highway in Brooklyn, and the Boston Post Road between New York City and Boston, Massachusetts.