Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Thompson Hollow | Valley | | Adams | 38 42 29 N | 083 23 24 W |
| Tiffin Elementary School | School | 293 | Adams | 38 47 49 N | 083 29 27 W |
| Tolle Hill | Summit | 341 | Adams | 38 56 48 N | 083 20 26 W |
| Township of Bratton | Civil | 279 | Adams | 39 00 53 N | 083 26 58 W |
| Township of Brush Creek | Civil | 349 | Adams | 38 47 52 N | 083 23 13 W |
| Township of Franklin | Civil | 223 | Adams | 39 00 21 N | 083 20 10 W |
| Township of Green | Civil | 241 | Adams | 38 41 06 N | 083 21 03 W |
| Township of Jefferson | Civil | 195 | Adams | 38 46 55 N | 083 19 44 W |
| Township of Liberty | Civil | 262 | Adams | 38 48 57 N | 083 37 46 W |
| Township of Manchester | Civil | 167 | Adams | 38 41 32 N | 083 36 22 W |
| Township of Meigs | Civil | 258 | Adams | 38 56 03 N | 083 23 33 W |
| Township of Monroe | Civil | 287 | Adams | 38 43 41 N | 083 30 58 W |
| Township of Oliver | Civil | 283 | Adams | 38 53 35 N | 083 31 23 W |
| Township of Scott | Civil | 211 | Adams | 38 57 02 N | 083 33 11 W |
| Township of Sprigg | Civil | 275 | Adams | 38 42 37 N | 083 37 46 W |
| Township of Tiffin | Civil | 255 | Adams | 38 48 19 N | 083 31 15 W |
| Township of Wayne | Civil | 285 | Adams | 38 52 14 N | 083 38 10 W |
| Township of Winchester | Civil | 296 | Adams | 38 57 20 N | 083 38 47 W |
| Tracey Run | Stream | | Adams | 38 40 33 N | 083 22 44 W |
| Tranquility | Populated Place | 236 | Adams | 38 57 45 N | 083 31 59 W |
| Tranquility Cemetery | Cemetery | 256 | Adams | 38 57 44 N | 083 31 52 W |
| Tranquility State Wildlife Area | Park | 258 | Adams | 38 59 02 N | 083 29 44 W |
| Tranquillity Post Office (historical) | Post Office | 236 | Adams | 38 57 45 N | 083 31 59 W |
| Treber Cemetery | Cemetery | 192 | Adams | 38 51 02 N | 083 29 13 W |
| Treber Run | Stream | | Adams | 38 51 00 N | 083 28 53 W |
| Trotter School (historical) | School | 200 | Adams | 38 46 03 N | 083 31 17 W |
| Truitt Hollow | Valley | | Adams | 38 44 13 N | 083 23 23 W |
| Tulip | Populated Place | 253 | Adams | 38 44 04 N | 083 24 54 W |
| Tulip Post Office (historical) | Post Office | 253 | Adams | 38 44 04 N | 083 24 54 W |
| Turkey Creek | Stream | | Adams | 38 50 12 N | 083 16 22 W |
| Turkey Creek Church | Church | 231 | Adams | 38 53 16 N | 083 22 30 W |
| Turkey Run | Stream | | Adams | 38 49 02 N | 083 18 08 W |
| Turkey Run | Stream | | Adams | 38 58 00 N | 083 39 42 W |
| Twin Creek Lookout Tower | Tower | 370 | Adams | 38 42 07 N | 083 16 53 W |
| Twin Creek Mission (historical) | Church | 174 | Adams | 38 39 08 N | 083 16 55 W |
| Twin Islands Campground | Locale | 153 | Adams | 38 41 43 N | 083 33 58 W |
| Union Hill Church | Church | 367 | Adams | 39 01 24 N | 083 17 03 W |
| United Brethren Cemetery | Cemetery | 264 | Adams | 38 52 00 N | 083 23 30 W |
| Unity | Populated Place | 290 | Adams | 38 53 30 N | 083 31 24 W |
| Unity Cemetery | Cemetery | 292 | Adams | 38 53 31 N | 083 31 24 W |
| Upper Blue Creek Tabernacle | Church | 247 | Adams | 38 44 23 N | 083 21 10 W |
| Upper Brush Creek School (historical) | School | 268 | Adams | 38 58 03 N | 083 39 13 W |
| Upper Georges Creek School (historical) | School | 256 | Adams | 38 58 12 N | 083 32 37 W |
| Upper Sister Creek | Stream | | Adams | 38 41 50 N | 083 29 51 W |
| Vastine Run | Stream | | Adams | 38 39 03 N | 083 16 53 W |
| Vaughns Chapel Cemetery | Cemetery | 270 | Adams | 38 51 09 N | 083 27 32 W |
| Waggoner Ripple (historical) | Populated Place | 158 | Adams | 38 42 45 N | 083 26 33 W |
| Waggoner Ripple Church | Church | 167 | Adams | 38 42 45 N | 083 26 29 W |
| Waggoner Ripple Post Office (historical) | Post Office | 158 | Adams | 38 42 45 N | 083 26 33 W |
| Waggoner Run | Stream | | Adams | 38 42 38 N | 083 26 44 W |
| Walker Hill | Summit | 324 | Adams | 38 54 29 N | 083 16 43 W |
| Walker Run | Stream | | Adams | 38 47 41 N | 083 18 57 W |
| Wallace Cemetery | Cemetery | 276 | Adams | 38 57 55 N | 083 39 10 W |
| Wamsley | Populated Place | 191 | Adams | 38 49 45 N | 083 16 37 W |
| Wamsley Cemetery | Cemetery | 194 | Adams | 38 50 13 N | 083 16 52 W |
| Wamsley Church | Church | 183 | Adams | 38 50 13 N | 083 16 46 W |
| Washburn Run | Stream | | Adams | 38 47 35 N | 083 40 37 W |
| Wayne Elementary School | School | 281 | Adams | 38 53 23 N | 083 36 54 W |
| Weasel Run | Stream | | Adams | 39 01 16 N | 083 26 18 W |
| Weaver Hill | Summit | 337 | Adams | 38 56 48 N | 083 19 50 W |
| West Fork Ohio Brush Creek | Stream | | Adams | 38 56 12 N | 083 28 07 W |
| West Union | Populated Place | 290 | Adams | 38 47 40 N | 083 32 43 W |
| West Union Church of the Nazarene | Church | 286 | Adams | 38 47 38 N | 083 32 41 W |
| West Union Elementary School | School | 295 | Adams | 38 47 32 N | 083 32 51 W |
| West Union High School | School | 292 | Adams | 38 47 32 N | 083 32 48 W |
| West Union Post Office | Post Office | 291 | Adams | 38 47 48 N | 083 32 47 W |
| West Union Presbyterian Church | Church | 287 | Adams | 38 47 36 N | 083 32 38 W |
| West Union United Methodist Church | Church | 292 | Adams | 38 47 43 N | 083 32 40 W |
| Wheat Ridge | Populated Place | 289 | Adams | 38 53 03 N | 083 30 12 W |
| Wheat Ridge | Ridge | 287 | Adams | 38 53 13 N | 083 29 26 W |
| Wheat Ridge Chapel | Church | 299 | Adams | 38 53 12 N | 083 30 30 W |
| Whippoorwill | Populated Place | 203 | Adams | 38 49 56 N | 083 30 11 W |
| Whippoorwill School (historical) | School | 212 | Adams | 38 50 03 N | 083 30 14 W |
| White Oak Cemetery | Cemetery | 237 | Adams | 38 50 00 N | 083 21 20 W |
| White Oak Chapel | Church | 236 | Adams | 38 50 02 N | 083 21 15 W |
| White Oak School (historical) | School | 238 | Adams | 38 50 00 N | 083 21 16 W |
| Wideawake School (historical) | School | 267 | Adams | 38 49 07 N | 083 33 42 W |
| Wikoff Run | Stream | | Adams | 38 38 56 N | 083 20 46 W |
| Wild Duck Branch | Stream | | Adams | 38 45 49 N | 083 42 15 W |
| Williamson Hollow | Valley | | Adams | 38 41 51 N | 083 36 29 W |
| Willow Grove School (historical) | School | 214 | Adams | 39 02 16 N | 083 25 26 W |
| Winchester | Populated Place | 296 | Adams | 38 56 30 N | 083 39 03 W |
| Winchester Cemetery | Cemetery | 296 | Adams | 38 56 18 N | 083 38 52 W |
| Winchester Elementary School | School | 297 | Adams | 38 56 30 N | 083 39 12 W |
| Winchester Lake | Reservoir | 292 | Adams | 38 56 48 N | 083 40 06 W |
| Winchester Lake Dam | Dam | 292 | Adams | 38 56 48 N | 083 40 06 W |
| Winchester Post Office | Post Office | 290 | Adams | 38 57 10 N | 083 38 14 W |
| Winterstein Cemetery | Cemetery | 351 | Adams | 38 45 40 N | 083 16 58 W |
| Winterstein Run | Stream | | Adams | 38 47 11 N | 083 19 14 W |
| Winterstein School (historical) | School | 232 | Adams | 38 46 18 N | 083 17 52 W |
| Wolf Creek | Stream | | Adams | 38 59 31 N | 083 25 50 W |
| Woolard Elementary School | School | 170 | Adams | 38 41 37 N | 083 36 26 W |
| WRAC-FM (West Union) | Tower | 334 | Adams | 38 51 25 N | 083 36 38 W |
| Wrightsville | Populated Place | 153 | Adams | 38 42 10 N | 083 30 44 W |
| WVXM-FM (West Union) | Tower | 336 | Adams | 38 51 36 N | 083 36 42 W |
| Wyckoffs Landing | Locale | 149 | Adams | 38 38 41 N | 083 20 17 W |
| Wyckoffs Run | Stream | | Adams | 38 38 39 N | 083 20 14 W |
| Young Cemetery | Cemetery | 191 | Adams | 38 42 00 N | 083 24 22 W |
| Youngsville | Populated Place | 270 | Adams | 38 55 22 N | 083 34 03 W |
| Allen County | Civil | 268 | Allen | 40 46 00 N | 084 05 00 W |
| Allen County Courthouse | Building | 270 | Allen | 40 44 35 N | 084 06 20 W |
| Allen County Fairgrounds | Locale | 280 | Allen | 40 43 35 N | 084 03 13 W |
| Allen County Farm Park | Park | 272 | Allen | 40 45 47 N | 084 02 57 W |
| Allen County Home | Building | 267 | Allen | 40 47 20 N | 084 02 36 W |
| Allen East Elementary School | School | 302 | Allen | 40 42 22 N | 083 55 32 W |
| Allen East High School | School | 286 | Allen | 40 45 34 N | 083 57 08 W |
| Allen East Primary School | School | 287 | Allen | 40 45 36 N | 083 57 08 W |
| Allentown | Populated Place | 242 | Allen | 40 45 17 N | 084 11 41 W |
| Allentown Cemetery | Cemetery | 249 | Allen | 40 45 17 N | 084 11 47 W |
| Allentown Post Office (historical) | Post Office | 244 | Allen | 40 45 20 N | 084 11 40 W |