The next route William Barclay Parsons, Chief Engineer of the Rapid Transit Commission laid out while the IRT was being constructed was one that would weave through northern Manhattan, run down 9th Avenue, then veer west right up against the waterfront along West Street. Like the First Avenue Subway (Route #1), the Rapid Transit Commission and Public Service Commission did not consider it a priority (most likely because of the existing 9th Avenue elevated) and kept the plans on the back burner. The IND however would give life to certain stretches of it. Read more after the jump.
This line was most likely intended to replace the 9th Avenue Elevated whose alignment Route #2 mimics from 110th Street to Gansevoort Street. Route #2 is indicated in red and the 9th Ave el is in blue.
In upper Manhattan, the IND's route seems to cover more territory, but the hilly topography of upper Manhattan is such, that a walk up a block could feel like a mile. (Or at least that's the impression I get whenever I go up there.) If anyone from the neighborhood can say that Parson's plan is better than the IND's plan, then by all means expound.
The Route #2 would be mimicked by the IND from 173rd Street to 124th Street. From there it runs diagonally under Morningside Park to Columbus/9th Avenue where it would run under or entirely replace the 9th Ave El.
At Gansevoort Street, Route #2 takes a radical departure and runs beneath West Street, right up against Hudson River shore. Perhaps it was intended to serve New Jersey ferry commuters and longshoremen working the docks.
Finally, it turns east into Battery Place where it seems to meet with the terminal of the First Avenue Subway (Route #1). It's interesting to imagine perhaps a through terminal where trains could run back and forth from 9th to 1st Avenues.