Maryland - Significance region: Local
| Hendler Creamery |
| Henry's Grove |
| Hermitage, The |
| Hidden Valley Farm |
| Highbarger, Jacob, House |
| Highfield House |
| Highland Lodge |
| Hilleary, William, House |
| Hill House |
| Hills, Dales, and the Vineyard |
| Hilltop Manor |
| Hippodrome Theatre |
| Hirsch Residence |
| Hobson's Choice |
| Hochschild, Kohn Belvedere and Hess Shoes |
| Hocking House |
| Hoffman Farm |
| Hoffman, Isaac, House |
| Hogmire-Berryman Farm |
| Hollins-Roundhouse Historic District |
| Holy Cross Roman Catholic Church |
| Home of the Friendless |
| Honeysuckle Lodge |
| Hood College Historic District |
| Hooper, James E., House |
| Hopeful Unity |
| Hopewell |
| Hotel Kernan |
| House at 9 North Front Street |
| Houses At 16-22 East Lee Street |
| Howard Lodge |
| Howard Park P.S. 218 |
| Howard's Inheritance |
| Huckleberry Hall |
| Hughes A.M.E. Chapel |
| Hull Memorial Christian Church |
| Hutzler Brothers Palace Building |
| Hyattsville Historic District |
| Iglehart |
| Indian Range |
| Industrial Building |
| Iron Hill Cut Jasper Quarry Archeological Site |
| ISLAND BELLE |
| Ivory Mills |
| Jackson, Lillie Carroll, House |
| Jena |
| Jericho Farm |
| Jerusalem Mill Village |
| Johnsontown Tobacco Barn No. 2 |
| Johnson-Wolfe Farm |
| Johnston Building |
| Joshua's Meadows |
| Katcef Archeological Site |
| Keating House |
| Keedysville Historic District |
| Keefer-Brubaker Farm |
| Kefauver Place |
| Kennersley |
| Kernan, James Lawrence, Hospital |
| Kingston |
| Kirk, Elisha, House |
| Kitterman-Buckey Farm |
| Klots Throwing Company Mill |
| Knipp, George, & Brother Building |
| Koons, Jacob, Farm |
| Koon, Thomas, House |
| Krieger, Seymour, House |
| Krug Iron Works |
| LaGrange |
| Lake Drive Apartments |
| Lake-Evesham Historic District |
| Lake Roland Historic District |
| Langley Park |
| Lankford House |
| Lansdowne |
| Lantz-Zeigler House |
| Lauraville Historic District |
| Laurel High School |
| Lauretum |
| Lawn, The |
| Lawyers Hill Historic District |
| Leadenhall Street Baptist Church |
| Legg's Dependence |
| Lehman's Mill Historic District |
| Leitersburg Historic District |
| Leverton, Jacob and Hannah, House |
| Lewis Mill Complex |
| Lexon |
| Lime Kiln Bottom |
| Linchester Mill |
| Linden |
| Linden Grove |
| Lindens, The |
| Lineboro Historic District |
| Linganore Farm |
| Linnwood |
| Linthicum Heights Historic District |
| Linthicum Walks |
| Lion Brothers Company Building |
| Little Elk Farm |
Data from United States Park Service and Wikidata
