- La Grange
- La Grange Park
- La Harpe
- La Moille
- La Prairie
- La Rose
- La Salle
- Lacon
- Ladd
- Lafayette
- Lake Barrington
- Lake Bluff
- Lake Camelot
- Lake Catherine
- Lake Forest
- Lake Holiday
- Lake in the Hills
- Lake Ka-Ho
- Lake of the Woods
- Lake Petersburg
- Lake Summerset
- Lake Villa
- Lake Zurich
- Lakemoor
- Lakewood Shores
- Lanark
- Langleyville
- LaPlace
- Latham
- Lawrenceville
- Le Roy
- Leaf River
- Lebanon
- Lee
- Leland
- Leland Grove
- Lemont
- Lena
- Lenzburg
- Leonore
- Lerna
- Lewistown
- Liberty
- Libertyville
- Lily Lake
- Limestone
- Lincoln Park
- Lincoln Square
- Lincolnwood
- Lindenhurst
- Lisbon
- Litchfield
- Little York
- Liverpool
- Loami
- Lockport
- Loda
- Logan
- Logan Square
- Lomax
- London Mills
- Long Creek
- Long Grove
- Long Lake
- Long Point
- Longview
- Loraine
- Lost Nation
- Lostant
- Loves Park
- Lovington
- Lower West Side
- Ludlow
- Lyndon
- Lynnville
- Lynwood
- Lyons
