Colorado - Role: Building
| Hynes, Thomas, House |
| I and M Building |
| Ideal Building |
| Iglesia de la Inmaculada Concepcion |
| Iglesia de San Francisco de Assisi |
| Iglesia de San Pedro y San Pablo |
| Iliff Hall |
| Indian Park School |
| IOOF Hall |
| Jackson, F.A., House |
| Jackson, George, House |
| Jacobs Building |
| Jacoe Store |
| Jaffa Opera House |
| Jamaica Primary School |
| James, Harry C., House |
| Jamestown Mercantile Building |
| Jamestown Town Hall |
| Jefferson Denver South Park and Pacific Railroad Depot |
| John and Nettie Kirtley House |
| Joshel, Lloyd M., House |
| Joslin Dry Goods Company Building |
| J. Warner Mills House |
| Kauffman House |
| Kauffman, William, House |
| Keating, Jeffery and Mary, House |
| Keck Homestead |
| Kelley House |
| Kelley-McDonald House |
| Kenjockety |
| Kennicott Cabin |
| Kerr House |
| Kettle-Jens House |
| Key Savings and Loan Association Building |
| Keystone Hotel |
| King, Dr. Alexander T., House and Carriage House |
| Kinner, John, House |
| Kissock Block Building |
| Kistler-Rodriguez House |
| Kistler Stationery Company Building |
| Kittredge Building |
| Knearl School |
| Knights of Pythias (KP) Building |
| Knight-Wood House |
| Kohn House |
| Kopper's Hotel and Saloon |
| Kullgren House |
| Lackner's Tavern |
| La Fave Block |
| Lafayette House |
| La Hacienda |
| La Jara Depot |
| Lake Agnes Cabin |
| Lamme Hospital |
| Land's End Observatory |
| Lang, William, Townhouse |
| LaSalla House |
| Las Animas Post Office |
| Las Feminilas Concilio #6 |
| Lathrop, J. V., House |
| Latuda, Frank, House |
| La Veta Pass Narrow Gauge Railroad Depot |
| La Vista Motel |
| Lay School |
| Leadville National Fish Hatchery |
| Lebanon School |
| Leeman Auto Company Building |
| LeFevre, Owen E., House |
| Leiffer House |
| Lennox House |
| Lett Hotel |
| Lewis, A. T., and Son Department Store |
| Lewis, A. T., New Building |
| Lewis House |
| Lewis, Inez Johnson, School |
| Lewis Mill |
| Limon Railroad Depot |
| Lincoln School |
| Lincoln School |
| Lincoln School |
| Lindley-Johnson-Vanderhoof House |
| Little Buckaroo Ranch Barn |
| Little Church in the Pines |
| Little Estate |
| Littlejohn Mine Complex |
| Littleton Creamery-Beatrice Foods Cold Storage Warehouse |
| Littleton Post Office |
| Littleton Town Hall |
| Livermore Hotel and General Store |
| Livestock Exchange Building |
| Logan County Courthouse |
| Loma Community Hall |
| Longmont Carnegie Library |
| Longmont College |
| Longmont Fire Department |
| Longmont Power Plant |
| Loretto Heights Academy |
| Lorraine Lodge |
| Louviers Village Club |
| Loveland Building and Coors Building |
Data from United States Park Service and Wikidata
