There is no post office at O’Hare but there are mail collection boxes scattered throughout the terminals: Terminal 1, Concourse B, Gate B9 Terminal 1, Concourse C, Gate C18 Terminal 3, Concourse H, Gate H1, Across from the Starbucks Terminal 3, Concourse L, Gate L2A, Across from Publican Tavern Terminal 5, Concourse M, Gate M8.
No post office at ORD Airport but you can drop mail off in the different mailboxes on site.
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