Manhattan 1880 Typographic Map Georeferenced on Modern Subway Map ( Well, Almost)

Using ARCGIS, I took a 1880 historic typographic map of Manhattan, available at the map center at the University of Texas at Austin, and georeferenced it onto my available shapefile maps of the subway system and subway stops and current street names.  I also included open space data as well.  I could not georeference perfectly and my maps are off by about a block.  This may be due to using a 1880 map or because may reference projects were not consistent or due to other errors. At any rate, the map shows that much of the lower East Side was formerly a marsh area prior to 1880?  My mistake may have been that I used the southern boundry of City Hall Park in 1880 which may not have been the same as it is now. The map is still interesting to look at.

In the map below, I focused on the Harlem area.  I brought in the shoreline and I made it red.  Notice that the area around the 148th Street - Lenox Terminal was marshland and the river bank was in a different location according to the 1880 map.

Another map of lower Manhattan.  Notice that in 1880, at least shown on the map, that the shoreline was more inland than today.  It is hard to tell if this 1880 map is showing the typology of 1880 or what was before.  Notice the marsh land near Fulton Street.

In the map below of Harlem, see the yellow pencil line that I added that is near East 107th Street.  Is this a stream that followed East 107th Street and emptied into the East River?  Notice that it crosses 110th Street and runs further north diagonally.  Is this a stream or a depression?

In the map below, which I got off the web, is an ancient British invasion map of Manhattan Island.  I circled that mysterious water flow in Harlem near East 107th Street in Green.  Is this an accurate deduction?