Using the footprints of parking lots and garages drawn into OpenStreetMap as a data source, the area of land in Chicagoland occupied by parking lots and garages is 247,539,968 square feet. (The data was exported using HOT Export Tool; you can replicate my export.)

That converts to:

  • 5,682.71 acres
  • 8.88 mi^2 (square miles)
  • 22.99 km^2 (square kilometers)
  • ≈ 0.26 × area of Manhattan (≈ 87 km^2 )
  • 3.9% area of Chicago is parking (Chicago is ~589.56 km^2 )

(I forgot to measure the portion of this within Chicago, and now the data snapshot is gone. I fixed this in the 2019 report.)