Pennsylvania - Significance region: National
| Grumblethorpe Tenant House |
| Halfway Lake Dam |
| Hammerstein, Oscar, II, Farm |
| Harmony Historic District |
| Harper, Frances Ellen Watkins, House |
| Harriman Historic District |
| Harrisburg Central Railroad Station and Trainshed |
| Harris, John, Mansion |
| Harvard, David, House |
| Harvey, William, House |
| Hatfield House |
| Hawk Mountain Sanctuary District |
| Hayhurst Farm |
| Head House Square |
| Heinz, H.J., Company |
| Herr, Hans, House |
| Hershey, Milton S., Mansion |
| Hessian Powder Magazine |
| Hill-Physick House |
| Historic Moravian Bethlehem Historic District |
| Homestead High-Level Bridge |
| Homestead Historic District |
| Honey Hollow Watershed |
| Hope Lodge |
| Hopewell Furnace National Historic Site |
| Horseshoe Curve |
| Hovenden House, Barn and Abolition Hall |
| Howell House |
| Independence National Historical Park |
| Independent Congregational Church |
| Institute of the Pennsylvania Hospital |
| Insurance Company of North America Building |
| Irish, Nathaniel, House |
| Ivy Mills Historic District |
| Johnson, John, House |
| Johnstown Flood National Memorial |
| Johnstown Flood National Memorial |
| Johnstown Inclined Railway |
| Keith House-Washington's Headquarters |
| Kennywood Park |
| Kooser State Park Family Cabin District |
| Kuerner Farm-Wyeth, Andrew, Studio |
| Kuster Mill |
| Lackawanna County Courthouse and John Mitchell Monument |
| Lafayette's Quarters |
| Lancaster City Historic District |
| Lancaster Watch Company |
| Landis Valley Museum |
| Lane House |
| Laurel Hill Cemetery |
| Laurel Hill RDA |
| Lawrence Park Historic District |
| Lazaretto, The |
| Leap-the-Dips |
| Legionville |
| Lehigh Canal |
| Lehigh Canal; Allentown to Hopeville Section |
| Lehigh Canal: Eastern Section Glendon and Abbott Street Industrial Sites |
| Leidy, Dr. Joseph, House |
| Leiper, Thomas, Estate |
| LeMoyne, F. Julius, House |
| Lesley, J. Peter, House |
| Lightfoot Mill |
| Linn Run State Park Family Cabin District |
| Lits Department Store |
| Locomotive No. 6755 |
| Logans Ferry Powder Works Historic District |
| Longland |
| Longwood Gardens District |
| Lukens Historic District |
| Main Building, U.S. Bureau of Mines |
| Marine Barracks |
| Marine Corps Supply Activity |
| Marshall, Humphry, House |
| Marshall, Humphry, House |
| Martin, C.F. & Company. |
| Mask and Wig Club of the University of Pennsylvania |
| Masonic Temple |
| Masonic Temple and Scottish Rite Cathedral |
| Massey, Thomas, House |
| Mauch Chunk and Summit Hill Switchback Railroad |
| Maxwell, Ebenezer, House |
| McCoy House |
| McKees Rocks Bridge |
| Meadowcroft Rockshelter |
| Meason, Isaac, House |
| Memorial Hall |
| Mennonite Meetinghouse |
| Mercer Museum |
| Merion Cricket Club |
| Merion Friends Meeting House |
| Merion Golf Club, East and West Courses |
| Metropolitan Opera House |
| Mikado Freight Locomotive No. 520 |
| Mikveh Israel Cemetery |
| Millanville-Skinners Falls Bridge |
| Mill Grove |
| Mill-Rae |
| Mine Roof Simulator |
| Minisink Archeological Site |
Data from United States Park Service and Wikidata
