“Twenty short blocks equal a mile” is an indispensable rule of thumb for judging distances in Manhattan, a convenient side benefit of the grid.
In the 1811 plan, the commissioners determined that cross-town streets should be 60 feet wide and that the blocks between them should measure about 200 feet on their eastern and western sides. By this metric, 20 short blocks add up to only 5,200 feet—just short of a mile—except that the commissioners also determined that 15 of the cross-town streets should be 100 feet wide, which supplies the extra distance. Walking at a comfortable pace and factoring in some time spent waiting for traffic lights to change, a New Yorker can expect to cover a block a minute on foot, another useful rule for estimating travel time.
The record for the Fifth Avenue Mile, an annual road race that uses the 20 blocks between East 80th Street and East 60th Street as its course, is 3:47.52, set by Sydney Maree in 1981. Organized by the New York Road Runners, the event draws thousands of runners to the route along Central Park, where they measure themselves against the grid. CY