| Subdivision Name | Code | Plat Vol | Plat Page | Document Number |
| I.F. BRUMMEL'S SUB | BRM IF | 54 | 18 | |
| I.M. HOWELL'S SUB | HOWL IM | 1 | 23* | |
| I.S. BARTLETT'S ADD | BART ISA | 4 | 82 | |
| I.S. BARTLETT'S SUB | BART ISS | 5 | 24 | |
| IDLEWILD ADD | IDLWLD | 2 | 59 | |
| IHC GROUP SUBDIVISION | IHCGRP | A547 | A | 2001K115667 |
| IL RT 64-SMITH ROAD SUB | ILRT64SR | 643 | B | 91K55800 |
| IL WATCH CASE CO'S ADD | ILWTCSC | 14 | 4 | |
| ILLINOIS IRON & BOLT | ILIR&BOC | 25 | 9 | |
| ILLINOIS PARK 2ND ADD | ILPK 2 | 11 | 13 | |
| ILLINOIS PARK ADD | ILPK | 10 | 5 | |
| INDIAN CREEK OF | INCKLL 1 | 71 | 12 | |
| INDIAN CREEK OF | INCKLL 2 | 72 | 22 | |
| INDIAN CREEK SUB | INCK | 36 | 18 | |
| INDIAN TERRACE | INTER | 35 | *34 | |
| INDIAN TRAIL ESTATES | INTRET 2 | A55 | A&B | 96K077150 |
| INDIAN TRAIL ESTATES | INTRET 3 | A56 | A&B | 96K077152 |
| INDIAN TRAIL ESTATES | INTRET | 44 | 4 | |
| INDIAN TRAIL ESTATES | INTRET 1 | 842 | A&B | 94K033844 |
| INDIAN TRAIL SUB UNIT 2 | INTR 2 | 515 | A&B | 90K04325 |
| INDIAN TRAIL WEST | INTRW 1 | 45 | 20 | |
| INDIAN TRAIL WEST | INTRW 1/ | 51 | 38 | |
| INDIAN TRAIL WEST | INTRW 10 | 66 | B | 1500778 |
| INDIAN TRAIL WEST | INTRW 11 | 352 | B | 1899612 |
| INDIAN TRAIL WEST | INTRW 2 | 48 | 27 | |
| INDIAN TRAIL WEST | INTRW 3 | 49 | 32 | |
| INDIAN TRAIL WEST | INTRW 4 | 54 | 16 | |
| INDIAN TRAIL WEST | INTRW 5 | 57 | 31 | |
| INDIAN TRAIL WEST | INTRW 6 | 63 | 26 | |
| INDIAN TRAIL WEST | INTRW 7 | 118 | A | 1543250 |
| INDIAN TRAIL WEST | INTRW 8 | 323 | B | 1868457 |
| INDIAN TRAIL WEST | INTRW 9 | 66 | A | 1500777 |
| INDUSTRIAL ADD | INDL | 7 | 66 | |
| INDUSTRIAL HARD CHROME | INDLHC | 673 | A | 92K13260 |
| INGHAM PARK SUBDIVISION UNIT 1 (AMENDED PLAT) | INGHAMPK1A | | | 2007K068661 |
| INGHAM PARK SUBDIVISION UNIT 1 (OLD PLAT) | INGHAMPK1 | | | 2007K007194 |
| INGLENOOK UNIT 1 | INGNK 1 | 49 | B | 1489176 |
| INNES & COULTER'S ADD | INN&COU | 1 | 43 | |
| INNES & COULTER'S SUB | INN&COUS | 1 | 44 | |
| INSTITUTE ADD | INST | 1 | 39 | |
| INSTITUTE PLAZA SUBDIVISION | INSTPZ | | | 2007K040422 |
| INTERNAL COMBUSTION SUBDIVISION | INTERNALCOMB | | | 2010K032638 |
| IOWA ADD | IOWA | 11 | 31 | |
| ISLAND ADD | ISLD | 5 | 74 | |
| ISLAND AVE ADD | ISLDAV | 21 | 16 | |
| ISLAND PARK FARMS | ISLDPKF | 26 | 15 | |
| IVAN KIRK'S SUB UNIT 1 | KIRK I 1 | 164 | A | 1622980 |
| IVY GLEN CONDO #1 | IVGCOND 1 | 52 | *37 | |
| IVY GLEN CONDO #2 | IVGCOND 2 | 52 | *49 | |
| IVY GLEN CONDO #3 | IVGCOND 3 | 52 | *59 | |
| IVY GLEN CONDO #4 | IVGCOND 4 | 52 | *66 | |
