Barrios de Illinois O

• O'Fallon (46)
• O'Hare (9)
• Oak Park (102)
• Old Irving Park (15)
• Old Town (124)
• Outer Loves Park/Machesney Park (9)
• Outer Northwest Rockford (38)
• Outer Rock Island/Moline (13)
• Outer South Rockford (19)
• Overlook (5)