Figure: Manhattan’s Expanding Footprint.
This map shows Manhattan’s expanding footprint over the 19th century. The increase in population and the development of mass transit around 1830 allowed for a dramatic northward movement of the population. Before that, New York was a walking city and expansion occurred rather slowly. Source: Robert Ernst’s book, Immigrant life in New York City, 1825-1863 (1949) and the Taylor map of 1879.