Chicago streets are laid out in a grid system. The starting (Baseline) point is the intersection of Madison 0 N&S & State 0 E&W. All addresses are ordered from that starting point and radiate outward N, S, E, and W from that intersection. Just like a grid system in mathematics, coordinates are found based on an X and Y Axis. X = North and South Addresses and Y = East & West Addresses (not to be confused with X-LO and X-HI on a PDT screen).

For example if you navigate the cities grid system and go to 300 South (Y Coordinate) and 1300 West (X Coordinate), you will arrive at the Police Academy at the Intersection of Jackson & Throop.

Each one-mile section of street is divided into eight blocks. Each has a series of “100” numbers reserved for addressing. Although 100 numbers are reserved, generally each block only goes up to 60 which leaves an extra 40 numbers as a buffer in case of diagonal streets and/or elongated blocks.

For example building addresses on a one-block stretch, in most cases, will begin at 0 and end at 59. There are exceptions, in which case the addresses on a block will exceed 59. For example building addresses on a one-block stretch on a diagonal street, such as Milwaukee Ave., will begin at 0 and can go as high 99.

Even Numbered Addresses will always be found on the North and West sides of a street.

Odd Numbered Addresses will always be found on the South and East sides of a street.