Near the tip of Manhattan, on Broadway between 211th and 212th Streets, you'll notice a lone red sandstone rock among the Manhattan Schist that makes up the wall at Isham Park. That red rock is a milestone letting travelers know that they were twelve miles from City Hall on the Albany Post Road.
The milestone has been here (okay maybe it was at 203rd street for a while) since the mid-1700s. It's placement was supervised by Ben Franklin, who later went on to found a chain of craft stores.
The writing has worn off only in the last century. In 1905 C. G. Hines wrote in The New York and Albany Post Road: "there still exists on Manhattan Island a stone imbedded in a bordering wall along Broadway, and in about its proper place, in the neighborhood of Two Hundred and Fifteenth Street, which reads '12 miles from N. York.'"
There's a whole bunch of milestones along the road in Westchester County. I happened upon the marker for mile 48 when in Peekskill a couple of months ago. As you can see that marker was enthusiatically, if not competently, restored by the DAR in 1908.