Codes for CTA stations?

I'm working on a new Chicago section for my transit-photography site, The Schumin Web Transit Center. Previously, the only rapid-transit system that's had significant coverage is Washington DC. There, each station has a code, officially an "RTU number", which gives each station a number based on route and sequence. Thus, for instance, Dupont Circle is A03, and the big transfer stations have two codes - one for each level (Metro Center is A01 and C01). I use these RTU numbers in the database on my site as an identifier, and it works quite well.

Does Chicago have a system like this?

I don't think Chicago has any sort of numbering system, although there are others here who have more hands-on experience with the CTA than I do. In opinion, it would be hard for the CTA to maintain such a system because stations here have had more openings and closures over the years. For example, if two stations in a row on the Green Line are numbered G7 and G8 and a new one opens in between them, what would its number be? G7.5 or G8, and G8 becomes G9? I bet the system works well for the WMATA because it's quite a bit newer and if the people planning it did their homework correctly, there's a smaller chance of a station closing down.

Maybe they could number them based on mileposts, like highway ramps?

The stations may be named by street location. Then you can't confuse the Pulaski station on the Orange, Red, Blue lines. Most Chicago residents know the 00/00 point is at State & Madison. Most streets south of there will be numbered, north of there all names. If you get a number 4000 E something it will be somewhere in the lake. 4000W takes you to Pulaski. Western Ave may be the longest street from N to S in the city. I may forget how many el stations are on or near Western Ave.

Computer routing systems take you to the downtown station where you can transfer from one line to another. Your whole trip can include any bus segments. For the price of the base fare + the transfer fee, a rider can continue their journey for the same price. In my day, you could go a long way for just a quarter extra. I could start at Midway and end up in Rosemont to go to the hobby show. In a AB station system, you may also have to change from the A train to the following B train that does stop at the station you wanted.

CTA does have station codes. They are used by the Revenue Department to keep track of how many fares come thru each station. They were assigned sometime in the 1960's, and since stations have been closed (and a few added) since, the list is someway erratic. However, unfortunately I do NOt have a listing.