OK class, are you ready to learn Chicago’s grid system?

Remember graph paper from middle school math? Then you can imagine the Chicago grid.

It has a north-south axis, and an east-west axis. The center point is at State and Madison in the heart of the Loop. That’s 0 north, south, east and west.

Each street address contains a directional prefix —N, S, E or W.

A mile is roughly eight city blocks. So, say you walk eight blocks north from Madison on State — you’ll be at 800 North State.

Eight blocks west of State on Madison — that’s right, you’re at 800 West Madison.

Head eight blocks east of State on Madison … Well, I hope you can swim.

Now let’s find some iconic Chicago locations.

Wrigley Field is located at 1060 West Addison at the intersection of Addison and Clark.  Addison is 3600 North, or 36 blocks north of Madison.

The 1060 West tells us the address is between 10 and 11 blocks west of State street on Addison  — that is, if State went that far north.

Now let’s visit Guaranteed Rate Field, home of the White Sox, at 333 West 35th St.

So, 35th Street is 35 blocks south of Madison. The 333 means it’s just over three blocks west of State Street.

Therefore, the Cubs and Sox play about the same distance from city center, on opposite sides of town.

Who can we thank for such a practical, math-oriented plan? A private citizen from Rogers Park, Edward Brennan.

He proposed the idea in 1901 to clean up what had been a confusing and chaotic system with repeated street names and addresses that were, well, all over the map.

Before we go, let’s navigate to one more location: 5400 N. St. Louis Avenue.

That’s exactly 54 blocks north of Madison at St. Louis Avenue, which is 3500  or 35 blocks west of State Street. It’s also home to our beloved WTTW studio.

Of course, there are exceptions to every rule — some addresses fall outside the grid structure, just like some hot dogs have ketchup.

But we’ll save that lesson for another day.