Ohio - Criteria: A (event)
| Hunter, Norvall, Farm |
| Huntington Inn, Old |
| Hunts Corners |
| Hunt-Wilke Farm |
| Huron County Children's Home |
| Huron Harbor Light |
| Ida Street Viaduct |
| Ideal Department Store Building |
| Idora Park |
| Immaculate Conception Church |
| Immaculate Conception Church, School, and Rectory |
| Immaculate Conception Rectory at Botkins |
| Imperial Glass Company |
| Independent Order of Odd Fellows Temple |
| Independent School District No. 2 Building |
| Indian Mill |
| Indianola Junior High School |
| Ingersoll, Cyrus J., House |
| Insco Apartments Building |
| Interurban Bridge |
| Inverness Club |
| Irishtown Bend Archeological District |
| Iutzi, Christian, Farm |
| Jackson Jr. High School |
| Jacob's Church |
| Jaeger Machine Company Office Building |
| Jaite Mill Historic District |
| Jamestown Opera House |
| Jefferson Avenue Historic District |
| Jefferson Schoolhouse |
| Jefferson Town Hall |
| Jeffrey, Malcolm, House |
| Jeffrey Manufacturing Company Office Building |
| Jersey Independent Order of Odd Fellows Hall |
| John Bright No. 1 Iron Bridge |
| Johnson-Campbell House |
| Johnson, E. J., House |
| Johnson Island Civil War Prison and Fort Site |
| Johnson Steel Street Railway Company General Offices Building |
| Johnston, William C., House And General Store |
| Jones, Elam, Public House |
| Jones Hall, Youngstown State University |
| Joseph-Cherrington House |
| Julian and Kokenge Company |
| Jyurovat Farmstead |
| Karamu House |
| Karrer, Henry, House |
| Kauffman, Linus B., House |
| Kaufman, Frank J., House |
| Kelleys Island South Shore District |
| Kelley, William, Hardware Store-Hayesville Odd Fellows Hall |
| Kendall, Virginia, State Park Historic District |
| Kenilworth Avenue Historic District |
| Kennel, John, Jr., Farm |
| Kennel, John Sr., Farm |
| Kent Industrial District |
| Kenton Public Library |
| Kerber's Marine Grocery |
| Kidwell Covered Bridge |
| Kilgore Union Presbyterian Church |
| Kilpi Hall |
| Kimball House |
| Kindleberger, Frederick, Stone House and Barn |
| King, George W., Mansion-Etowah |
| Kinney, James, Farmstead |
| Kinsey, The |
| Kirby, James, Mill |
| Kirby Road School |
| Kirtland Temple |
| Kister Mill |
| Knapp, William, House |
| Knights of Pythias Hall |
| Knowlton Covered Bridge |
| Knowlton, Dr. William A., House |
| Krause Building-Otto Moser's Cafe |
| Kuebeler-Stang Block |
| Kundtz, Theodor, Company Building |
| Kunkle Log House |
| Ladd's Tavern |
| Lafayette Lodge No. 79 |
| Lagonda Club Building |
| Lagonda National Bank |
| Lakefork School |
| Lake Hamilton Dam |
| Lake Shore and Michigan Southern (LS&MS) Railroad Depot-Wauseon |
| Lake Shore And Michigan Southern Passenger Depot |
| Lake Shore And Michigan Southern Railroad Depot |
| Lake Shore Bank and Cleveland Public Library St. Clair Branch |
| Lake Shore & Michigan Southern Railroad Station |
| Lake Township School |
| Lambert, Jeremiah, House and Barn |
| Landmark Tavern |
| Lane's Mill Historic Buildings |
| Lange Hotel |
| Lanning, T., & Co. Department Store |
| Lanterman Mill |
| Laughlin, Homer, House |
| Laurel Homes Historic District |
| Lavin, Carl and Audrey, House |
| Law, Henry, Farm Historic District |
Data from United States Park Service and Wikidata
