Northeast - steepest street close to NY City: Elm Av?

Elm Avenue in Ridgefield NJ is about 3 miles from Manhattan -- see on map (http://maps.google.com/maps/ms?ie=UTF8&hl=en&msa=0&msid=115487569681665383360.0004581387a8e25de20ef&ll=40.835031,-73.993692&spn=0.008523,0.015514&z=16).
It has 125 vertical feet at a steepness around 18% grade, including a little "step" around 25% (and then another little step).

I was riding around Ridgefield exploring different roads, started climbing Elm east from Shaler Blvd. At first gentle, then moderate, then steep . . . and then I could see what was above and I couldn't believe it. So I turned off climbed Ray Av instead and did some more exploring.
I came back and tried again, but when I reached the little "step", I lost confidence and stepped off my bike and walked to the top (so I could get good data for my GPS), then rode back down Ray. Tried again and this time I made it pedaling. But that little "step" is the steepest asphalt I've ever ridden up. It was pretty near the limit of my strength to keep the pedals turning.
I would not ride down it -- each time I took Ray Av just south of it instead -- which itself has a short section around 16% or more, so too steep for some people to descend on their bike, I guess walking is an alternative.I didn't see any climbs close to the City steeper than that on the NYCC regional grades table -- though I've heard there's a steep climb in some park in northern Manhattan -- but maybe it's not really a street?
GPS -- It was one of the first hills I've measured with my GPS with a barometric altimeter. Even with my GPS unit designed to measure elevation accurately (because the GPS satellite system itself is not designed for that), I still got somewhat inconsistent results (from five data "track" sequences for the same hill). Which gives me even less confidence than I had previously in steepness numbers reported by people using a normal GPS unit (which lacks a barometric altimeter).Ken

I didn't see any climbs close to the City steeper than that on the NYCC regional grades table -- though I've heard there's a steep climb in some park in northern Manhattan -- but maybe it's not really a street?

There' a section on the bike path that runs past the Little Red Lighthouse and under the GWB, and then rises up to the Henry Hudson Parkway. If you were to follow the route over the pedestrian bridge and out onto the streets, it will eventually take you to the GWB, on the right, or Bennet Park (http://en.wikipedia.org/wiki/Bennet_Park) to the left, which is the highest point in Manhattan at 265 feet.

It's not a street and I have no idea what the average gain might be, but it's a pretty steep climb in some places.

Looking at Delorme Topo, Elm from Shrader to the end gives an average grade of 9%. I'm inclined to take my GPS altimeter with a grain of salt as it is affected by barometric pressure and I never take the time (or have the data) to calibrate it. FWIW the NYCC site gives an average grade of 7.1% to the Alpine Approach Rd. When I used to have the grade displayed on my Edge it would jump as high as 14% in some spots. The hill on the Hudson River Greenway just past the little red lighthouse would get as high as 20%, and while some people go by average it is those little steep steps that kill me.