All - Constructed - 1900–1909
| Leominster High School |
| Leonard, J.T and Anna, House |
| Leon Grange No. 795 |
| Letchworth State Park |
| Lewis, Charles D., House |
| Lewis, Frank T. and Polly, House |
| Lighthouse Inn |
| Lincoln, Abraham, Statue |
| Lincoln County Courthouse |
| Lincoln Liberty Life Insurance Building |
| Lincoln National Bank |
| Lincoln School |
| Lincoln School |
| Linde Air Products Factory |
| Liston Range Front Lighthouse |
| Little Missouri River Bridge |
| Little Rock Central High School |
| Lockman, Jacob P. House |
| Lodge |
| Lodge Zare Zapadu No. 44 |
| Logan County Courthouse |
| Logan LDS Sixth Ward Church |
| Logan, Leonard M., House |
| Logging Creek Ranger Station Historic District |
| Lohr, Charles and Mary, House |
| Lomb, Adolph, House |
| Lombard, Alvin O., House |
| Lone Star Baptist Church |
| Longfellow, Henry Wadsworth, Memorial |
| Long, George Parker, House |
| Long, McCorkle and Murray Houses |
| Longmont Fire Department |
| Long Shoals Bridge |
| Lopez, Hilario, House |
| Lorenz Hotel |
| Lorraine Apartments |
| Los Angeles Pacific Company Ivy Park Substation |
| Lostine Pharmacy |
| Lougee, George A., House |
| Louise Cotton Mill |
| Louisiana Public Library |
| Louisville and Nashville Railroad Depot |
| Louisville Free Public Library |
| Lovejoy, Carrie, House |
| Lowenstein, Abraham, House |
| Lowndes County Courthouse |
| Lowney Chocolate Factory |
| Lucas Mansion |
| Luft, Conrad, Sr., House |
| Luke, Arthur F., House |
| Lukins, F. L., House |
| Lumsden, W. H., House |
| Lundwall, Charles, Building |
| Lutheran Indian Mission |
| Lynchburg Hosiery Mill No. 1 |
| Lynn Item Building |
| Lynn Realty Company Building No. 2 |
| Lytle, Joseph, Home |
| Macy, R. H., and Company Store |
| Madison Candy Company |
| Madison County Courthouse |
| Madison Gas and Electric Company Powerhouse |
| Madison-Putnam-60th Place Historic District |
| Madisonville Bank |
| Madsen, David and Evinda, House |
| Mahler and Carolina Trust Buildings |
| Mahned Bridge |
| Mahnomen County Courthouse |
| Mahoning County Courthouse |
| Main Building, Blinn College |
| Maine Historical Society |
| Main Hall/La Crosse State Normal School |
| Main Street Station and Trainshed |
| Malmborg School |
| Manchester Schoolhouse |
| Mancos High School |
| Mandel Brothers Warehouse Building |
| Manhattan Carnegie Library Building |
| Manhattan Hotel |
| Manito Park and Boulevard |
| Mann, Horace, School |
| Manning Water Tower |
| Mansuy and Smith Automobile Showroom Building |
| Marathon Motor Works |
| Marcia Browne Junior High School |
| Marconi Wireless Station Site |
| Maria Angelorum Chapel |
| Marion County Courthouse |
| Market Street Bridge |
| Marquis Opera House |
| Marshall, David, House |
| Marsh, George B., Building |
| Martens, Julius J., Company Building |
| Martin, Darwin D., House |
| Martinez, Teodoro, House |
| Marx, Albert and Theresa, House |
| Mary Island Light Station |
| Masonic Temple |
| Masonic Temple |
| Masonic Temple Building |
Data from United States Park Service and Wikidata
