Fair Lawn, New Jersey is the place where I am from. Fair Lawn has two claims to fame. The first claim is Radburn, a pre-Depression planned community. The second claim is its street addresses, many of which are number-dash-number.
Today through the help of Google of course I decided to find out why Fair Lawn uses this system. Here’s what I learned from Bergen.com:

Fair Lawn uses a unique* house-numbering system. Homes here carry hyphenated numbers; the first numbers corresponding to the block-distances from Broadway (going north) and from the Passaic River (going east); the numbers after the dash, counting mostly by fours, refer to the house number.

*According to Wikipedia, Queens, NY uses a similar system.

Now I understand what the numbers mean. But now that I understand what the numbers mean, I realize what I really want to know. Why the dash?