Barrios de Illinois O

• O'Fallon (24)
• O'Hare (8)
• Oak Lawn (23)
• Oak Park (104)
• Old Farm (1)
• Old Irving Park (12)
• Old Town (125)
• Old Towne (1)
• Outer Loves Park/Machesney Park (9)
• Outer Northwest Rockford (24)
• Outer Rock Island/Moline (8)
• Outer South Rockford (16)
• Overlook (1)