Maryland - Criteria: A (event)
| Gaithersburg B & O Railroad Station and Freight Shed |
| Gaithersburg Latitude Observatory |
| Gandy Belting Company Building |
| Garrett County Courthouse |
| Garrett Park Historic District |
| Gladden Farm |
| Glebe House |
| Glencoe |
| Glen Echo Park Historic District |
| Glenn Dale Tuberculosis Hospital and Sanatorium |
| Glen Oak Hotel |
| Glenview Farm |
| Glyndon Historic District |
| Gompers School |
| Goucher College |
| Grace Episcopal Church Complex |
| Graceham Moravian Church And Parsonage |
| Granite Historic District |
| Grassland |
| Graystone Lodge |
| Greater Homeland Historic District |
| Greenbelt Historic District |
| Green's Inheritance |
| Green Spring Valley Historic District |
| Grief, L. and Bro., Inc. Manufactory |
| Guilford |
| Guilford Historic District |
| Gunpowder Meetinghouse |
| Gunther Brewing Company |
| Hager House |
| Hagerstown Armory |
| Hagerstown Charity School |
| Hagerstown City Park Historic District |
| Hagerstown Commercial Core Historic District |
| Hagerstown Historic District |
| Half-Way House |
| Hammond Wood Historic District |
| Hampden Historic District |
| Hampstead School |
| Hampton National Historic Site |
| Hancock's Resolution |
| Hanover Farm House |
| Harford Furnace Historic District |
| Harford National Bank |
| Harrington |
| Harris Farm |
| Havre de Grace Historic District |
| Havre de Grace Lighthouse |
| Hebrew Orphan Asylum |
| Heiser, Rosenfeld, and Strauss Buildings |
| Hendler Creamery |
| Hermitage, The |
| Hessian Barracks |
| Highland Lodge |
| HILDA M. WILLING |
| Hilleary, William, House |
| Hilltop Manor |
| Hippodrome Theatre |
| Hitt's Mill and Houses |
| Hochschild, Kohn Belvedere and Hess Shoes |
| Hoffman Farm |
| Hoffman, Isaac, House |
| Hogmire-Berryman Farm |
| Hollins-Roundhouse Historic District |
| Holly Hill |
| Holy Cross Roman Catholic Church |
| Home of the Friendless |
| Hood College Historic District |
| Hooper Island Light Station |
| Hooper, James E., House |
| Hope House |
| Hopewell |
| Houses At 16-22 East Lee Street |
| Howard Park P.S. 218 |
| HOWARD (Skipjack) |
| Howard Street Tunnel |
| Hughes A.M.E. Chapel |
| Hull Memorial Christian Church |
| Hutzler Brothers Palace Building |
| Hyattsville Armory |
| IDA MAY |
| Indian Queen Tavern and Black's Store |
| Industrial Building |
| Inns on the National Road |
| ISLAND BELLE |
| ISLAND BIRD (log canoe) |
| ISLAND IMAGE (log canoe) |
| ISLAND LARK (log canoe) |
| Ivory Mills |
| JAY DEE (log canoe) |
| Jericho Covered Bridge |
| Jericho Farm |
| Jerusalem Mill Village |
| Johns Hopkins Hospital Complex |
| Johnson-Wolfe Farm |
| Kaese Mill |
| KATHRYN |
| Keedy House |
| Keedysville Historic District |
| Keefer-Brubaker Farm |
Data from United States Park Service and Wikidata
