Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Willard Elementary School | School | 227 | Kane | 41 59 43 N | 088 17 58 W |
| Willard Elementary School | School | 211 | Rock Island | 41 29 47 N | 090 30 45 W |
| Willard Grove Cemetery | Cemetery | 162 | Will | 41 26 29 N | 088 13 58 W |
| Willard Landing | Locale | 104 | Union | 37 27 19 N | 089 27 03 W |
| Willard Methodist Church | Church | 190 | Cook | 41 52 08 N | 087 47 35 W |
| Willard School | School | 224 | Champaign | 40 07 05 N | 088 13 54 W |
| Willard School | School | 181 | Cook | 41 48 19 N | 087 36 39 W |
| Willard School (historical) | School | 260 | Boone | 42 19 41 N | 088 43 32 W |
| Willaredt Lake | Reservoir | 156 | Madison | 38 48 18 N | 089 51 54 W |
| Willaredt Lake Dam | Dam | 156 | Madison | 38 48 18 N | 089 51 54 W |
| Willeford | Populated Place | 134 | Williamson | 37 39 22 N | 088 51 06 W |
| Willey Cemetery | Cemetery | 193 | McDonough | 40 17 19 N | 090 42 01 W |
| Willeys | Populated Place | 192 | Christian | 39 35 49 N | 089 14 00 W |
| Willhoit Airport | Airport | 187 | Macoupin | 39 02 44 N | 089 50 26 W |
| William Beye Elementary School | School | 189 | Cook | 41 53 27 N | 087 46 57 W |
| William Carr Cemetery | Cemetery | 201 | Rock Island | 41 28 39 N | 090 32 30 W |
| William Carr School (historical) | School | 211 | Rock Island | 41 29 37 N | 090 31 39 W |
| William Creek | Stream | | Perry | 38 00 14 N | 089 20 03 W |
| William E Dever Crib Light | Locale | 180 | Cook | 41 55 00 N | 087 39 19 W |
| William E Koenig Airport | Airport | 195 | Jersey | 39 00 58 N | 090 19 05 W |
| William Green Homes (subdivision) | Populated Place | 179 | Cook | 41 54 17 N | 087 38 44 W |
| William H Althoff Park | Park | 228 | McHenry | 42 21 08 N | 088 17 03 W |
| William H Ray Public School | School | 180 | Cook | 41 47 33 N | 087 35 40 W |
| William Harris Elementary School | School | 207 | Macon | 39 51 47 N | 088 56 57 W |
| William Hatch Elementary School | School | 190 | Cook | 41 54 19 N | 087 46 58 W |
| William Jones Commercial High School | School | 180 | Cook | 41 52 26 N | 087 37 40 W |
| William L Rutherford Airport | Airport | 191 | Whiteside | 41 42 05 N | 089 49 44 W |
| William Leonard Public Library | Building | 185 | Cook | 41 38 26 N | 087 42 31 W |
| William Nashold Elementary School | School | 243 | Winnebago | 42 13 30 N | 089 03 27 W |
| William Nisbet Cemetery | Cemetery | 180 | Cass | 39 54 47 N | 090 16 02 W |
| William Quinton RLA Airport | Airport | 217 | McLean | 40 16 55 N | 089 01 45 W |
| William Rainey Harper College | School | 235 | Cook | 42 04 53 N | 088 04 15 W |
| William Rainey Harper Memorial Library | Building | 180 | Cook | 41 47 16 N | 087 35 59 W |
| William Rush Vocal Studio | School | 183 | Cook | 41 52 36 N | 087 37 28 W |
| William Shed School (historical) | School | 225 | Pope | 37 32 00 N | 088 34 32 W |
| William Stratton State Access Area | Park | 153 | Grundy | 41 21 19 N | 088 25 04 W |
| William W Fox Childrens Center | Hospital | 193 | Livingston | 41 05 37 N | 088 25 40 W |
| William W Kimball House | Building | 181 | Cook | 41 51 28 N | 087 37 14 W |
| William Watkins School (historical) | School | 171 | Menard | 40 05 40 N | 089 54 47 W |
| William Wieboldt Hall | Building | 180 | Cook | 41 47 16 N | 087 36 01 W |
| William Wood Cemetery | Cemetery | 188 | Greene | 39 25 22 N | 090 29 56 W |
| Williams Academy | School | 225 | DuPage | 41 50 55 N | 088 07 21 W |
| Williams Airpark | Airport | 163 | Morgan | 39 45 15 N | 090 21 55 W |
| Williams Building | Building | 182 | Cook | 41 52 49 N | 087 38 03 W |
| Williams Camp (historical) | Locale | 183 | Fayette | 39 03 48 N | 088 54 23 W |
| Williams Cemetery | Cemetery | 149 | Fayette | 38 50 38 N | 089 14 49 W |
| Williams Cemetery | Cemetery | 146 | Jefferson | 38 19 14 N | 088 49 31 W |
| Williams Cemetery | Cemetery | 223 | Lee | 41 39 45 N | 089 24 30 W |
| Williams Cemetery | Cemetery | 140 | Perry | 38 06 46 N | 089 12 03 W |
| Williams Cemetery | Cemetery | 149 | Pope | 37 18 35 N | 088 31 31 W |
| Williams Cemetery | Cemetery | 145 | St. Clair | 38 39 21 N | 089 49 57 W |
| Williams Cemetery | Cemetery | 168 | Union | 37 30 15 N | 089 10 43 W |
| Williams Cemetery | Cemetery | 127 | Wayne | 38 35 44 N | 088 15 45 W |
| Williams Chapel | Church | 131 | Franklin | 38 07 07 N | 088 51 44 W |
| Williams Church | Church | 119 | Jackson | 37 52 10 N | 089 13 33 W |
| Williams College | School | 181 | Cook | 41 47 57 N | 087 36 11 W |
| Williams Creek | Stream | | Schuyler | 40 15 03 N | 090 50 30 W |
| Williams Creek | Stream | | Washington | 38 20 17 N | 089 34 01 W |
| Williams Ditch | Canal | 190 | Kankakee | 41 10 08 N | 087 32 06 W |
| Williams Elementary School (historical) | School | 183 | Cook | 41 50 38 N | 087 37 44 W |
| Williams Family Cemetery | Cemetery | 220 | Adams | 39 53 31 N | 091 05 51 W |
| Williams Family Cemetery | Cemetery | 214 | Knox | 40 55 57 N | 090 01 25 W |
| Williams Family Cemetery | Cemetery | 120 | White | 38 00 47 N | 088 06 59 W |
| Williams Hall | Building | 238 | McLean | 40 30 29 N | 088 59 23 W |
| Williams Hall | Building | 183 | Peoria | 40 41 50 N | 089 36 48 W |
| Williams Hill | Summit | 325 | Pope | 37 34 56 N | 088 28 32 W |
| Williams Hollow | Valley | | Jersey | 38 59 26 N | 090 33 18 W |
| Williams Hollow School (historical) | School | 143 | Jersey | 38 59 20 N | 090 31 49 W |
| Williams Landing Strip | Airport | 203 | Douglas | 39 44 40 N | 087 58 55 W |
| Williams Love Park | Park | 223 | DuPage | 41 46 11 N | 087 59 07 W |
| Williams Mill (historical) | Locale | 196 | Livingston | 40 52 42 N | 088 37 46 W |
| Williams Park | Park | 214 | Winnebago | 42 21 36 N | 089 03 14 W |
| Williams Park | Park | 225 | Winnebago | 42 17 27 N | 089 05 09 W |
| Williams Park | Populated Place | 229 | Lake | 42 15 15 N | 088 11 00 W |
| Williams Prairie Church | Church | 135 | Williamson | 37 50 46 N | 088 50 58 W |
| Williams School | School | 130 | Pope | 37 34 36 N | 088 26 12 W |
| Williams School (historical) | School | 225 | Brown | 39 59 20 N | 090 53 18 W |
| Williams School (historical) | School | 175 | Fayette | 39 04 17 N | 089 07 13 W |
| Williams School (historical) | School | 188 | Fulton | 40 31 55 N | 090 21 34 W |
| Williams School (historical) | School | 125 | Hamilton | 38 04 03 N | 088 27 22 W |
| Williams School (historical) | School | 167 | Jefferson | 38 25 03 N | 088 56 24 W |
| Williams School (historical) | School | 202 | Macoupin | 39 09 35 N | 089 48 35 W |
| Williams School (historical) | School | 144 | Perry | 38 06 50 N | 089 12 07 W |
| Williams School (historical) | School | 215 | Pike | 39 40 38 N | 091 02 53 W |
| Williams School (historical) | School | 180 | Rock Island | 41 43 47 N | 090 15 24 W |
| Williams School (historical) | School | 180 | Scott | 39 43 00 N | 090 27 22 W |
| Williams School (historical) | School | 212 | Vermilion | 40 17 05 N | 087 48 51 W |
| Williams School (historical) | School | 121 | White | 38 13 40 N | 088 11 02 W |
| Williams-Edwards Cemetery | Cemetery | 196 | Greene | 39 30 22 N | 090 25 16 W |
| Williams-Edwards Cemetery | Cemetery | 196 | Greene | 39 30 22 N | 090 25 15 W |
| Williamsburg | Populated Place | 149 | Jefferson | 38 13 40 N | 089 03 31 W |
| Williamsburg | Populated Place | 210 | Moultrie | 39 43 03 N | 088 34 19 W |
| Williamsburg (historical) | Populated Place | 206 | Shelby | 39 17 43 N | 088 56 15 W |
| Williamsburg (subdivision) | Populated Place | 214 | Cook | 42 03 43 N | 088 00 55 W |
| Williamsburg Green | Populated Place | 275 | Kane | 42 01 50 N | 088 21 07 W |
| Williamsburg Hill | Populated Place | 235 | Shelby | 39 18 01 N | 088 56 05 W |
| Williamsburg Square Park | Park | 200 | Cook | 42 08 58 N | 087 48 41 W |
| Williamsfield | Populated Place | 215 | Knox | 40 55 21 N | 090 00 52 W |
| Williamsfield High School | School | 214 | Knox | 40 55 37 N | 090 01 18 W |
| Williamson | Populated Place | 184 | Madison | 38 59 08 N | 089 45 50 W |
| Williamson Airport | Airport | 202 | Cumberland | 39 19 08 N | 088 25 30 W |
| Williamson Airport | Airport | 192 | Shelby | 39 27 37 N | 088 52 06 W |
| Williamson Cemetery | Cemetery | 185 | Jackson | 37 52 22 N | 089 26 00 W |
| Williamson Cemetery | Cemetery | 189 | Montgomery | 39 07 29 N | 089 18 34 W |
| Williamson County | Civil | 131 | Williamson | 37 44 00 N | 088 56 00 W |
| Williamson County Courthouse | Building | 135 | Williamson | 37 43 50 N | 088 55 37 W |
| Williamson County Fairgrounds | Park | 133 | Williamson | 37 43 55 N | 088 54 45 W |
| Williamson County Regional Airport | Airport | 143 | Williamson | 37 45 11 N | 089 00 41 W |
| Williamson Dam | Dam | 186 | Madison | 38 59 24 N | 089 45 30 W |
| Williamson School (historical) | School | 147 | Jefferson | 38 16 46 N | 088 43 33 W |