Cargo increased 20% yr over yr 2014-2015.
According to most recent FAA stats
Chicago OHare is 4th largest cargo airport (by lbs)after Anchorage, Memphis(FDX), Louisville(UPS)
4 IL ORD Chicago O'Hare International Chicago (2015)9,063,805,029 (2014)7,541,411,779 +20.19%
That new Northern Cargo terminal my be needed soon
Edit: BTW: Chicago-Rockford is 31st in nation.