In most U.S. cities with which I have had any contact, there is a fairly straightforward building numbering scheme. In Portland, Oregon and many other cities, buildings are numbered based on their distance from certain base streets or avenues, generally at the rate of 100 numbers per block. In San Francisco this is not the case, instead building numbers start at the beginning of a street and continue until the street ends, which is a scheme with its own charm and lack of practicality, but it is at least consistent.

Manhattan, on the other hand, has this, the Manhattan Address Algorithm, which is a sort of formula for determining the cross street for any Manhattan address. The formula involves dividing the address by 20 and then adding a special number which varies by avenue; then there are exceptions to even this arcane rule. I presume, if a new building were added that didn’t already have an address, the new address would have to fit into this algorithm as well.

Can anyone tell us where this numbering scheme comes from, when and why it was adopted? Manhattan north of 14th Street is pretty regularly laid out, why not just a grid of numbers that matches from avenue to avenue?

Puzzled in Peoria