O'Hare is about 7,627 acres, or 11.25 square miles. That roughly covers the area from the Loop north to Diversey, and west to Humboldt Park.

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The facility moves more than 66 million people per year, making it a pretty sizable city in more ways than just its acreage.

There are also 25,863 parking spaces and a whopping 229,355 square feet of green roofs.

For more information, check out city-data.com.