Section
Counties
"What county is this city in" lookups -- including the cities that straddle more than one county, which a one-line answer usually misses.
What County Is Chicago In?
Chicago is entirely inside Cook County -- all 84 of its ZIP codes, no split with a neighboring county. Cook is the second-most-populous county in the US, and it's losing that spot to Houston's Harris County.
What County Is Houston In?
Houston is entirely inside Harris County, its address labeled that way for every one of the city's 178 ZIP codes -- and Harris County is about to overtake Chicago's Cook County as the second most populous county in the US.