A few parts of Chicago near O'Hare airport are in DuPage county. In California a city by law cannot cross a county line. San Francisco has a unified city/coun

A few parts of Chicago near O'Hare airport are in DuPage county. In California a city by law cannot cross a county line. San Francisco has a unified city/county government. That's why it's the Board of Supervisors. I think Miami/Dade County is similar.