Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Union Church | Church | 34 | Anne Arundel | 39 02 56 N | 076 34 44 W |
| Union Church | Church | 172 | Baltimore | 39 30 10 N | 076 29 43 W |
| Union Church | Church | 0 | Calvert | 38 42 15 N | 076 31 60 W |
| Union Church | Church | 19 | Caroline | 38 53 55 N | 075 43 47 W |
| Union Church | Church | 82 | Cecil | 39 38 48 N | 075 54 32 W |
| Union Church | Church | 1 | Dorchester | 38 27 34 N | 075 55 40 W |
| Union Church | Church | 17 | Harford | 39 31 10 N | 076 08 33 W |
| Union Church | Church | 22 | Kent | 39 16 21 N | 076 05 30 W |
| Union Church | Church | 15 | Queen Anne's | 39 11 27 N | 076 00 60 W |
| Union Church | Church | 182 | Washington | 39 32 29 N | 077 38 49 W |
| Union Church | Church | 14 | Wicomico | 38 18 29 N | 075 34 40 W |
| Union Church | Church | 4 | Worcester | 38 05 29 N | 075 30 57 W |
| Union Church (historical) | Church | 0 | Somerset | 38 04 59 N | 075 51 44 W |
| Union Corner | Locale | 20 | Caroline | 39 01 39 N | 075 48 19 W |
| Union Corner | Populated Place | 20 | Caroline | 39 01 38 N | 075 48 19 W |
| Union Corners | Populated Place | 18 | Caroline | 38 54 01 N | 075 43 50 W |
| Union Dam | Dam | 69 | Baltimore | 39 17 42 N | 076 46 47 W |
| Union Dam | Dam | 62 | Howard | 39 17 40 N | 076 46 48 W |
| Union Ferry | Locale | 3 | Wicomico | 38 20 31 N | 075 41 44 W |
| Union Franklin City Cemetery | Cemetery | 6 | Worcester | 38 01 25 N | 075 23 56 W |
| Union Greenbackville Cemetery | Cemetery | 6 | Worcester | 38 00 46 N | 075 24 38 W |
| Union Grove Cemetery | Cemetery | 238 | Allegany | 39 42 12 N | 078 41 58 W |
| Union Grove Cemetery | Cemetery | 17 | Caroline | 38 45 38 N | 075 52 42 W |
| Union Hall (historical) | Building | 135 | Baltimore | 39 23 30 N | 076 34 24 W |
| Union Hills | Populated Place | 186 | Carroll | 39 36 00 N | 077 08 60 W |
| Union Hospital | Hospital | 9 | Cecil | 39 36 30 N | 075 49 58 W |
| Union Medical Clinic | Hospital | 14 | Harford | 39 32 42 N | 076 05 27 W |
| Union Meeting House (historical) | Church | 301 | Garrett | 39 28 49 N | 079 04 07 W |
| Union Memorial Cemetery | Cemetery | 20 | Caroline | 39 01 52 N | 075 49 15 W |
| Union Memorial Cemetery | Cemetery | 19 | Caroline | 38 53 55 N | 075 43 46 W |
| Union Memorial Church | Church | 44 | Anne Arundel | 38 55 47 N | 076 37 58 W |
| Union Memorial Hospital | Hospital | 63 | Baltimore (city) | 39 19 44 N | 076 36 51 W |
| Union Memorial Methodist Church | Church | 14 | Prince George's | 38 49 02 N | 076 45 20 W |
| Union Memorial United Methodist Church | Church | 53 | Baltimore (city) | 39 17 47 N | 076 39 25 W |
| Union Mills | Populated Place | 178 | Carroll | 39 40 11 N | 077 01 29 W |
| Union Mills (historical) | Building | 165 | Carroll | 39 40 07 N | 077 01 07 W |
| Union Mills Homestead Park | Park | 166 | Carroll | 39 40 03 N | 077 01 08 W |
| Union School (historical) | School | 84 | Cecil | 39 38 50 N | 075 54 32 W |
| Union School (historical) | School | 80 | Cecil | 39 37 47 N | 075 57 57 W |
| Union School (historical) | School | 10 | Cecil | 39 33 32 N | 075 56 59 W |
| Union School (historical) | School | 14 | Queen Anne's | 39 11 23 N | 076 00 20 W |
| Union Schoolhouse (historical) | School | 270 | Carroll | 39 30 46 N | 076 58 32 W |
| Union Square | Park | 30 | Baltimore (city) | 39 17 12 N | 076 38 29 W |
| Union Square United Methodist Church | Church | 24 | Baltimore (city) | 39 17 10 N | 076 38 24 W |
| Union Square-Hollins Market Historic District | Park | 25 | Baltimore (city) | 39 17 15 N | 076 38 19 W |
| Union Street United Methodist Church | Church | 239 | Carroll | 39 34 54 N | 076 59 60 W |
| Union Temple Baptist Church | Church | 60 | Baltimore (city) | 39 18 38 N | 076 38 11 W |
| Union United Methodist Church | Church | 3 | Caroline | 38 41 47 N | 075 46 29 W |
| Union United Methodist Church | Church | 0 | Somerset | 37 58 03 N | 076 01 24 W |
| Union United Methodist Church | Church | 3 | Talbot | 38 47 12 N | 076 13 33 W |
| Union United Methodist Church | Church | 15 | Wicomico | 38 27 07 N | 075 33 43 W |
| Union Valley | Populated Place | 81 | Cecil | 39 38 47 N | 075 54 34 W |
| Union Wesley United Methodist Church | Church | 2 | Queen Anne's | 38 58 26 N | 076 17 08 W |
| Uniontown | Populated Place | 200 | Carroll | 39 35 36 N | 077 06 58 W |
| Uniontown Academy (historical) | School | 197 | Carroll | 39 35 37 N | 077 06 54 W |
| Uniontown Cemetery | Cemetery | 195 | Carroll | 39 35 39 N | 077 06 36 W |
| Uniontown Elementary School | School | 196 | Carroll | 39 35 32 N | 077 07 00 W |
| Uniontown Historic District | Park | 200 | Carroll | 39 35 35 N | 077 07 06 W |
| Uniontown Post Office | Post Office | 197 | Carroll | 39 35 37 N | 077 06 55 W |
| Uniontown United Methodist Church | Church | 194 | Carroll | 39 35 38 N | 077 06 40 W |
| Unionville | Populated Place | 138 | Frederick | 39 28 29 N | 077 11 08 W |
| Unionville | Populated Place | 3 | Talbot | 38 48 48 N | 076 08 23 W |
| Unionville | Populated Place | 6 | Worcester | 38 03 38 N | 075 35 57 W |
| Unionville Heights | Populated Place | 4 | Worcester | 38 03 45 N | 075 35 47 W |
| Unionville Post Office | Post Office | 137 | Frederick | 39 28 30 N | 077 11 10 W |
| Unitarian Church of Anne Arundel | Church | 21 | Anne Arundel | 38 59 49 N | 076 31 09 W |
| Unitarian of Rockville Church | Church | 132 | Montgomery | 39 05 25 N | 077 09 48 W |
| Unitarian Universalist Church of God | Church | 181 | Washington | 39 39 05 N | 077 43 40 W |
| Unitarian Universalist Church of Silver Spring | Church | 99 | Montgomery | 39 01 31 N | 076 58 48 W |
| United Apostolic Church | Church | 4 | Dorchester | 38 33 21 N | 076 05 02 W |
| United Baptist Church | Church | 19 | Baltimore (city) | 39 18 05 N | 076 35 42 W |
| United Bible Way Church | Church | 127 | Baltimore (city) | 39 20 09 N | 076 39 40 W |
| United Brethren Cemetery | Cemetery | 332 | Frederick | 39 41 51 N | 077 27 23 W |
| United Church of the First Born | Church | 8 | Wicomico | 38 23 42 N | 075 36 13 W |
| United Communities volunteer fire department | Building | | Queen Anne's | 39 28 13 N | 076 34 23 W |
| United Evangelical Church | Church | 19 | Baltimore (city) | 39 16 54 N | 076 34 16 W |
| United Hebrew Cemetery | Cemetery | 36 | Baltimore | 39 14 28 N | 076 40 21 W |
| United Hebrew Cemetery | Cemetery | 24 | Baltimore | 39 19 09 N | 076 31 09 W |
| United Missionary Baptist Church | Church | 4 | Dorchester | 38 33 38 N | 076 05 04 W |
| United State Lifesaving Station Museum | Building | 3 | Worcester | 38 19 52 N | 075 05 10 W |
| United States Census Bureau | Building | 88 | Prince George's | 38 50 53 N | 076 55 40 W |
| United States Custom House | Building | 4 | Baltimore (city) | 39 17 17 N | 076 36 33 W |
| United States Department of Agriculture Research Center | Locale | 36 | Prince George's | 39 01 55 N | 076 53 04 W |
| United States Department of the Interior Patuxent Wildlife Research Center | Locale | 39 | Prince George's | 39 02 58 N | 076 48 15 W |
| United States Naval Academy | School | 4 | Anne Arundel | 38 58 55 N | 076 28 59 W |
| United States Naval Academy Dairy Farm | Locale | 49 | Anne Arundel | 39 03 30 N | 076 40 49 W |
| United States Naval Hospital | Hospital | 14 | Anne Arundel | 38 59 19 N | 076 29 29 W |
| United States Navy Oceanographic Office | Building | 89 | Prince George's | 38 50 45 N | 076 55 43 W |
| United States Navy Photo Interpretation Center | Building | 89 | Prince George's | 38 51 02 N | 076 55 59 W |
| United States Postal Training Facility | Locale | 100 | Montgomery | 39 01 17 N | 077 11 11 W |
| United States Public Health Services Hospital | Hospital | 62 | Baltimore (city) | 39 19 29 N | 076 37 26 W |
| United Steam Fire Engine Company Number 3 | Building | | Frederick | 39 41 23 N | 077 41 11 W |
| United Warren Methodist Church | Church | 126 | Montgomery | 39 09 53 N | 077 28 39 W |
| Unity | Populated Place | 164 | Montgomery | 39 13 34 N | 077 04 10 W |
| Unity Baptist Church | Church | 75 | Howard | 39 12 36 N | 076 43 52 W |
| Unity Christian Church | Church | 40 | Baltimore (city) | 39 17 42 N | 076 38 28 W |
| Unity Church | Church | 6 | Howard | 39 12 28 N | 076 42 23 W |
| Unity Methodist Church (historical) | Church | 13 | Dorchester | 38 38 07 N | 075 51 55 W |
| Universal Gospel Tabernacle | Church | 6 | Baltimore | 39 18 40 N | 076 27 34 W |
| Universalist Church (historical) | Church | 8 | Cecil | 39 31 52 N | 075 48 25 W |
| Universalist Church (historical) | Church | 21 | Cecil | 39 33 42 N | 075 48 31 W |
| University Baptist Church | Church | 71 | Baltimore (city) | 39 19 50 N | 076 37 02 W |
| University Christian Church | Church | 32 | Prince George's | 38 58 23 N | 076 57 04 W |
| University Gardens | Populated Place | 23 | Prince George's | 38 58 53 N | 076 58 12 W |
| University Hills Recreation Center | Park | 20 | Prince George's | 38 59 02 N | 076 57 39 W |
| University Hospital | Hospital | 17 | Baltimore (city) | 39 17 17 N | 076 37 27 W |
| University Nursing Home | Building | 123 | Montgomery | 39 02 12 N | 077 01 30 W |
| University of Baltimore | School | 20 | Baltimore (city) | 39 18 21 N | 076 37 00 W |
| University of Maryland | School | 27 | Prince George's | 38 59 09 N | 076 56 19 W |
| University of Maryland - Baltimore County Campus | School | 61 | Baltimore | 39 15 19 N | 076 42 42 W |