City w/ most crossings in usa?

There are 2273 grade crossings listed in the FRA database for the six counties that you listed.

Cook - 1327
DuPage - 184
Lake - 168
Will - 273
McHenry - 109
Kane - 212

If grade crossings only are being counted, not over/under crossings, then Houston wins the top billing with 906.

These totals include both freight and commuter crossings, yes? Is there a difference? Should there be a difference?

The data that I have posted includes road/rail crossings, regardless of the rail traffic type. Although I suspect that there is no freight on Amtrak’s tracks.

Grade crossings within the Chicago city limits are, with some exceptions, to be found primarily in areas of the city that didn’t get built up until after the First World War or in former industrial areas. The route of the Belt Railway of Chicago provides a rough approximation of the borders of the pre-WW1 built-up area of the city.

Wonder how many are in Louisville. I’m bound to get a pic of every one at some point.

If you meant Louisville, KY (and not Louisville, IL), there are 246 grade crossings, and 403 total crossings listed in the FRA database.

If you do include those five counties in a Los Angeles search, realize you are including a land area that is probably bigger than most states. San Bernardino County alone is bigger than many states. Much of it is desert and is much closer to Las Vegas than Los Angeles.