Since I ride past this hill often, I measured the grade on this hill with a level, measuring the height on the low side with the 4 foot level horizontal. (See other discussions in BF: the difference between measuring along the slope or measuring the horizontal distance is minor) Grade = height / horizontal distance
This is Monastery Street in Cincinnati. The bottom section is a consistent 18% grade. I can climb it quite easily in my 34 - 26 gear, but I'm balancing on the bike, going about 3 mph, with only one pedal stroke a second (30 rpm).
It's really difficult to show the grade. I kept the camera horizontal.
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I posted this link recently in BF. I really like this picture:
Check out Canton Avenue in Pittsburgh. It's 37%
They include it on the Dirty Dozen hill climb. Youtube video