Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Sixmile Prairie | Flat | 144 | Perry | 38 03 07 N | 089 33 47 W |
| Sixmile School (historical) | School | 239 | McLean | 40 33 42 N | 088 56 40 W |
| Sixmile Settling Basin | Basin | 139 | Pike | 39 26 53 N | 090 53 44 W |
| Sixmile Slough | Gut | 128 | Calhoun | 38 58 32 N | 090 33 28 W |
| Sixteen Cemetery | Cemetery | 213 | Edgar | 39 39 13 N | 087 38 06 W |
| Sixth Grace United Presbyterian Church | Church | 184 | Cook | 41 49 53 N | 087 36 42 W |
| Sixth Street Park | Park | 133 | Madison | 38 52 22 N | 090 05 08 W |
| Sixth Street School | School | 222 | Kane | 41 53 08 N | 088 18 47 W |
| Sixty-eighth Street Crib Light | Locale | 175 | Cook | 41 47 09 N | 087 31 54 W |
| Sixty-Fourth Street Beach Pavilion | Building | 179 | Cook | 41 46 53 N | 087 34 25 W |
| Sixty-seventh Street Beach | Beach | 177 | Cook | 41 46 28 N | 087 34 03 W |
| Sixtythird Street Park | Park | 206 | DuPage | 41 46 23 N | 088 03 27 W |
| Skaggs School (historical) | School | 140 | Williamson | 37 41 34 N | 088 56 58 W |
| Skare Estates | Populated Place | 241 | Ogle | 41 56 38 N | 089 09 10 W |
| Skatium Ice Arena | Building | 192 | Cook | 42 02 56 N | 087 44 59 W |
| Skeel School (historical) | School | 225 | Ford | 40 26 34 N | 088 24 12 W |
| Skelton | Populated Place | 186 | Logan | 40 08 34 N | 089 15 14 W |
| Skelton Cemetery | Cemetery | 185 | Logan | 40 08 42 N | 089 15 31 W |
| Skene Mine (historical) | Mine | 206 | Jo Daviess | 42 18 07 N | 090 14 12 W |
| Ski Hill | Populated Place | 265 | McHenry | 42 12 07 N | 088 12 25 W |
| Skiles Branch | Stream | | Fulton | 40 09 39 N | 090 16 15 W |
| Skiles Junior High School | School | 181 | Cook | 42 02 35 N | 087 42 29 W |
| Skillet Fork | Stream | | White | 38 07 53 N | 088 07 32 W |
| Skillet Fork Drainage Ditch | Canal | 113 | Wayne | 38 17 46 N | 088 27 59 W |
| Skillet Fork Farm Airport | Airport | 129 | Wayne | 38 17 45 N | 088 33 25 W |
| Skillet Fork Lagoon | Stream | | Wayne | 38 15 50 N | 088 25 03 W |
| Skinner Airport | Airport | 198 | La Salle | 41 14 15 N | 088 55 35 W |
| Skinner Classical Elementary School | School | 182 | Cook | 41 52 47 N | 087 39 33 W |
| Skinner Island | Island | 155 | Grundy | 41 23 20 N | 088 15 27 W |
| Skinner Park | Park | 181 | Cook | 41 52 47 N | 087 39 39 W |
| Skinner School (historical) | School | 194 | Christian | 39 23 35 N | 089 20 09 W |
| Skinner School (historical) | School | 217 | Livingston | 40 55 18 N | 088 18 12 W |
| Skinner School (historical) | School | 235 | McLean | 40 36 17 N | 088 56 44 W |
| Skinney Island | Island | 128 | Madison | 38 52 20 N | 090 09 03 W |
| Skokie | Populated Place | 185 | Cook | 42 02 00 N | 087 44 00 W |
| Skokie Central Congregation | Church | 184 | Cook | 42 02 02 N | 087 43 52 W |
| Skokie Country Club | Locale | 202 | Cook | 42 07 42 N | 087 45 43 W |
| Skokie Ditch | Canal | 190 | Cook | 42 05 33 N | 087 44 07 W |
| Skokie Junction | Populated Place | 207 | Lake | 42 15 33 N | 087 51 13 W |
| Skokie Junior High School | School | 191 | Cook | 42 06 19 N | 087 44 49 W |
| Skokie Lagoons | Reservoir | 189 | Cook | 42 06 06 N | 087 45 33 W |
| Skokie Manor | Populated Place | 206 | Lake | 42 14 38 N | 087 51 28 W |
| Skokie Northshore Sculpture Park | Park | 181 | Cook | 42 02 02 N | 087 42 38 W |
| Skokie Park Tennis Center | Park | 189 | Cook | 42 01 58 N | 087 45 12 W |
| Skokie Playfield Golf Club | Locale | 190 | Cook | 42 06 40 N | 087 45 31 W |
| Skokie Police Department | Building | 190 | Cook | 42 02 00 N | 087 45 27 W |
| Skokie Post Office | Post Office | 189 | Cook | 42 01 56 N | 087 45 07 W |
| Skokie Public Library | Building | 189 | Cook | 42 01 34 N | 087 45 29 W |
| Skokie River | Stream | | Cook | 42 05 15 N | 087 46 20 W |
| Skokie River Nature Preserve | Park | 204 | Lake | 42 15 45 N | 087 51 25 W |
| Skokie Sports Park | Park | 183 | Cook | 42 01 33 N | 087 42 57 W |
| Skokie Swift Station | Building | 191 | Cook | 42 02 26 N | 087 45 08 W |
| Skokie Valley Baptist Church | Church | 190 | Cook | 42 04 57 N | 087 45 18 W |
| Skokie Valley Hospital | Hospital | 194 | Cook | 42 03 20 N | 087 44 26 W |
| Skokie Valley Park | Park | 186 | Cook | 42 00 58 N | 087 44 37 W |
| Skokie Village Hall | Building | 189 | Cook | 42 01 34 N | 087 45 22 W |
| Skull Creek | Stream | | Shelby | 39 26 41 N | 088 44 18 W |
| Skunk Creek | Stream | | Mercer | 41 14 25 N | 090 37 11 W |
| Skunk Creek | Stream | | Whiteside | 41 53 06 N | 089 42 18 W |
| Skunk Hollow | Valley | | Carroll | 42 10 28 N | 089 58 16 W |
| Sky Harbor Airport (historical) | School | 206 | Cook | 42 08 35 N | 087 51 28 W |
| Sky Soaring Airport | Airport | 270 | Henry | 42 09 15 N | 088 30 41 W |
| Skyline Lake | Lake | 170 | Vermilion | 40 07 55 N | 087 43 20 W |
| Skyline Memorial Park | Cemetery | 238 | Will | 41 26 24 N | 087 44 18 W |
| Skyscraper Building | Building | 181 | Cook | 41 59 56 N | 087 39 23 W |
| Skyview Center | School | 246 | Winnebago | 42 10 20 N | 089 03 18 W |
| Slabtown School (historical) | School | 205 | Piatt | 40 04 08 N | 088 33 16 W |
| Slackwater (historical) | Populated Place | 199 | Stark | 40 58 57 N | 089 49 15 W |
| Slackwater Bridge | Bridge | 185 | Stark | 40 59 06 N | 089 49 27 W |
| Slade Branch | Stream | | Perry | 38 11 37 N | 089 20 54 W |
| Slade Cemetery | Cemetery | 138 | Jefferson | 38 18 38 N | 089 00 28 W |
| Slade School (historical) | School | 268 | DeKalb | 41 55 17 N | 088 48 10 W |
| Slade School (historical) | School | 157 | Washington | 38 13 46 N | 089 23 54 W |
| Slagel Strip | Airport | 205 | Livingston | 40 51 10 N | 088 50 55 W |
| Slagle Cemetery | Cemetery | 167 | Scott | 39 40 12 N | 090 30 10 W |
| Slagle School (historical) | School | 244 | Ogle | 42 03 06 N | 089 12 32 W |
| Slapout Mine | Mine | 133 | Pope | 37 31 06 N | 088 25 31 W |
| Slate Creek | Stream | | Jasper | 39 03 30 N | 088 14 40 W |
| Slater Creek | Stream | | Clark | 39 24 06 N | 087 53 58 W |
| Slater Creek | Stream | | Hancock | 40 17 29 N | 091 14 34 W |
| Slawson School (historical) | School | 131 | Perry | 38 01 02 N | 089 16 32 W |
| Sleepy Hollow | Populated Place | 225 | Kane | 42 05 39 N | 088 18 09 W |
| Sleepy Hollow | Populated Place | 163 | Williamson | 37 36 01 N | 088 56 57 W |
| Sleepy Hollow | Valley | | Mason | 40 10 30 N | 089 46 05 W |
| Sleepy Hollow (subdivision) | Populated Place | 181 | Cook | 41 48 51 N | 087 44 28 W |
| Sleepy Hollow Ditch | Stream | | Mason | 40 08 24 N | 089 43 26 W |
| Sleepy Hollow Elementary School | School | 236 | Kane | 42 05 19 N | 088 18 38 W |
| Sleepy Hollow Park | Park | 190 | Cook | 42 04 40 N | 087 48 11 W |
| Sleepy Hollow Park | Park | 195 | Lake | 42 12 09 N | 087 49 44 W |
| Sleepy Hollow School (historical) | School | 168 | Mason | 40 09 06 N | 089 44 06 W |
| Sleepy Hollow Village Hall | Building | 228 | Kane | 42 05 34 N | 088 18 55 W |
| Sleezer School (historical) | School | 232 | Kendall | 41 32 13 N | 088 32 50 W |
| Sleight Pond | Lake | 184 | Pike | 39 44 25 N | 090 43 34 W |
| Slick School (historical) | School | 265 | Carroll | 42 08 43 N | 089 54 36 W |
| Slifka Memorial Park | Park | 182 | Madison | 38 57 58 N | 089 45 30 W |
| Slim Lake | Lake | 133 | Fulton | 40 29 09 N | 089 54 24 W |
| Slim Lake (historical) | Lake | 131 | Fulton | 40 23 48 N | 090 01 41 W |
| Slim Lake (historical) | Lake | 128 | Scott | 39 40 52 N | 090 37 28 W |
| Slingerland Park | Park | 247 | Cook | 42 00 34 N | 088 04 55 W |
| Slip Number Eight | Locale | 175 | Cook | 41 40 59 N | 087 34 54 W |
| Slip Number Four | Locale | 175 | Cook | 41 40 40 N | 087 34 54 W |
| Slip Number Four | Locale | 175 | Cook | 41 42 20 N | 087 32 59 W |
| Slip Number One | Locale | 175 | Cook | 41 40 02 N | 087 35 21 W |
| Slip Number One (historical) | Locale | 179 | Cook | 41 42 45 N | 087 32 43 W |
| Slip Number Six | Locale | 175 | Cook | 41 40 49 N | 087 34 55 W |
| Slip Number Three | Locale | 175 | Cook | 41 40 17 N | 087 35 29 W |
| Slip Number Three | Locale | 175 | Cook | 41 42 27 N | 087 32 55 W |
| Slip Number Two | Locale | 175 | Cook | 41 40 29 N | 087 34 56 W |
| Slip Number Two | Locale | 178 | Cook | 41 42 34 N | 087 32 51 W |
| Sloan (subdivision) | Populated Place | 161 | Madison | 38 55 02 N | 090 09 00 W |