I've wondered this myself. Turns out Wikipedia has the answer: "Park Avenue was originally known as Fourth Avenue and carried the tracks of the New York and H

I've wondered this myself. Turns out Wikipedia has the answer: "Park Avenue was originally known as Fourth Avenue and carried the tracks of the New York and Harlem Railroad starting in the 1830s. The railroad originally built an open cut through Murray Hill, which was covered with grates and grass between 34th and 40th Street in the early 1850s. A section of this "park" was renamed Park Avenue in 1860. In 1867, the name applied all the way to 42nd Street. When Grand Central Depot was opened in the 1870s, the railroad tracks between 56th and 96th Streets were sunk out of sight, and, in 1888, Park Avenue was extended to the Harlem River." http://en.wikipedia.org/wiki/Park_Avenue_%28Manhattan%29#History http://en.wikipedia.org/wiki/Park_Avenue_%28Manhattan%29#His...