There are 77 numbered, official Community Areas, designated by the city; 75 of these were delineated in the 1920s by the Social Science Research Committee at the University of Chicago. No. 76, O'Hare, was designated when the city annexed that land; and no. 77, Edgewater, was split from Uptown in the 1980s.
You can find good maps on the
city web site.
However, these are mainly wide tracts of land within which are many individual neighborhoods, designated by local use, dreamed up by neighborhood associations, bestowed by Realtors and developers, etc. They have no official standing and their boundaries are often in flux. Where is New Town these days? Gone. And whether a residence is in Andersonville or Edgewater, Buena Park or Uptown may depend on whether you're buying or selling.
The Community Area called the Near North Side encompasses River North, Streeterville, the Gold Coast, Goose Island and several lesser known neighborhoods. But their boundaries don't match up neatly. By usage and custom, Streeterville runs from Michigan Avenue east to Lake Michigan (not exactly the area Capt. Streeter laid claim to, but close enough). River North, meanwhile, runs west from Wabash, according to the River North Association. So what do you call the area between Michigan and Wabash? Some call it the Magnificent Mile, a phrase coined by a developer, but technically that only refers to Michigan Avenue itself (although I have seen so-called neighborhood maps that made it a mile wide as well as a mile long).
Moreover, sometimes the Community Areas have the same names as smaller neighborhoods within them. The Loop Community Area, for example extends from the Chicago River south to Roosevelt Road, a far larger area than the original Loop as bounded by the L tracks over Wabash, Van Buren, Wells and Lake, or the somewhat wider neighborhood many people mean when they say "The Loop," which is bounded by the river on the north and west, the lake on the east and Congress Parkway on the south.
Also, the names don't always mean what you think they might. Peterson Park the neighborhood is nowhere near Peterson Park the park.
In the 1970s, the city compiled the map that John M refers to by sending out researchers who asked "What neighborhood is this?"
My suggestion would be to do something similar. Start with the Community Areas. In smaller neighborhoods, where you need a specific designation, call a neighborhood associaton or chamber of commerce for that area and ask them what boundaries they use. But there's plenty of disagreement and you'll have to come up with your own decisions. For example, many people seem to use North Avenue as the boundary between Bucktown and Wicker Park, but if you look at the maps on kiosks in the neighborhood, the dividing line is Wabansia. And I've seen the same restaurant described in different media as being in North Center, Ravenswood and Lake View.