Ohio - Area of significance: Commerce
| Greenfield Commercial Historic District |
| Greenville South Broadway Commercial District |
| Gregory House |
| Gross, L.N., Company Building |
| Haddon Hall |
| Haines, Frank, House |
| Halle Building |
| Halle's Shaker Square |
| Hamilton Downtown Historic District |
| Hamilton-Ickes House |
| Harding-Jones Paper Company District |
| Harmar Historic District |
| Harper-Cosgrave Block |
| Harrison National Bank |
| Hartman Hotel |
| Hart's Drug Store |
| Hartville Hotel |
| Hayden Building |
| Haydenville Historic Town |
| Headley Inn., Smith House And Farm |
| Herrold, Thomas Jefferson, House and Store |
| Hertzler, Daniel, House |
| High and Gay Streets Historic District |
| High Street Commercial Block |
| Hill, James Delos, House |
| Hillsboro Historic Business District |
| Hollencamp House |
| Hoover Company Historic District |
| Hostetter Inn |
| Hotel Manchester |
| Hotel Metropole |
| Hotel Rieger |
| Howard, Adam, House |
| Hoyt Block |
| Hudson Avenue Historic District |
| Hull, Isaac, Store |
| Hull-Wolcott House |
| Huron-Superior Streets Warehouse-Produce Historic District |
| Ideal Department Store Building |
| Jackson, Andrew, House |
| Jay's Lunch |
| Johnston, William C., House And General Store |
| Jones, Elam, Public House |
| Jones, Elijah Pelton, House |
| Kelley, Barney, House |
| Kelley, William, Hardware Store-Hayesville Odd Fellows Hall |
| Kelly Family Home |
| Kent Industrial District |
| Kenton Courthouse Square Historic District |
| Kerber's Marine Grocery |
| Kilbourn Commercial Building |
| Kinney, Eli, House |
| Kiser Mansion |
| Kishman Fish Company Buildings |
| Koch, John E., Jr., House |
| Kress Building |
| Kuebeler-Stang Block |
| Lagonda National Bank |
| Lake Shore And Michigan Southern Passenger Depot |
| Lake Shore Bank and Cleveland Public Library St. Clair Branch |
| Lakewood Downtown Historic District |
| Lancaster West Main Street Historic District |
| Landmark Tavern |
| Lange Hotel |
| Lanman-Ingram House |
| Lanning, T., & Co. Department Store |
| Latty, Judge Alexander, House |
| Laundon, Thomas W., House |
| Lebanon Commercial District |
| Liggett-Freedlander House |
| Limbach Block Historic District |
| Lindner Building |
| Lindsey Building |
| Lion Knitting Mills |
| Liquid Carbonic Corporation Dry Ice Plant |
| Lisbon Historic District |
| Lockington Locks Historical Area |
| Lock No. 26 |
| Lock No. 27 |
| Lock No. 28 |
| Lock No. 29 and Aqueduct |
| Lock No. 30 and Feeder Dam |
| Lock No. 31 |
| Lock No. 32 |
| Lock No. 33 |
| Lock No. 34 |
| Lock No. 35 |
| Lock No. 37 and Spillway |
| Lock No. 38 and Spillway |
| Lock No. 39 and Spillway |
| Lock Tender's House and Inn |
| Lockwood, J. C., House |
| Loew-Define Grocery Store and Home |
| Logan Historic District |
| Lorain Avenue Commercial Historic District |
| Lorain Station Historic District |
| Lotz, Henry, Stone |
| Louisville Historic District |
| Lower Prospect-Huron Historic District |
| Lubal Manufacturing and Distributing Company, The |
Data from United States Park Service and Wikidata
