Below, you can see the neighborhood of Marble Hill just across the river from the northern tip of Manhattan. A lot of people ask if I included this neighborhood in my walk. Marble Hill used to be part of Manhattan island; notice how the streets still curve to follow the original shoreline. In the early 19th century, a canal was dug just south of present day 225th Street, and Marble Hill itself became an island—cut off from the rest of Manhattan. Later, the original river to the north was filled in, and the neighborhood became part of the U.S. mainland, but it always remained part of the borough of Manhattan. I arbitrarily decided that my walk would just encompass the current island of Manhattan. Other outlying parts of the borough include Ellis, Liberty, Governors and Roosevelt Islands.