| Louisville Cement | Speed | IN |
| Louisville Insulation & Supply | Evansville | IN |
| Louisville & Nashville Railroad | Evansville | IN |
| Lowell High School | Lowell | IN |
| Ls Ayers & Company | Indianapolis | IN |
| LTV Steel | Youngstown | IN |
| LTV Steel | East Chicago | IN |
| Lucky Steer | Fort Wayne | IN |
| Luse Stevenson | Portage | IN |
| Luse Stevenson | Gary | IN |
| Lutheran Hospital | Fort Wayne | IN |
| Lutheran Hospital | Anderson | IN |
| Lynnville Coal | Lynnville | IN |
| Lyon & Greenleaf | Ligonier | IN |
| Maco | Shelbyville | IN |
| Maco | Huntington | IN |
| Madden Handle | Mount Vernon | IN |
| Madison Junior High School | Madison | IN |
| Madison Light & Railway | Madison | IN |
| Magic Builders Supply | Madison | IN |
| Magic City Builders & Supply | Muncie | IN |
| Magnavox | Fort Wayne | IN |
| Major Hospital | Shelbyville | IN |
| Manardo Fruit | Lafayette | IN |
| Manchester College | North Manchester | IN |
| Manon Siding | Indianapolis | IN |
| Mansfield Engineering | Indianapolis | IN |
| Maple Street Waste Water Treatment Plant | Galveston | IN |
| Maplewood Animal Clinic | Muncie | IN |
| Marblehead Lime | Gary | IN |
| Marbon | Gary | IN |
| Marburger Supply | Peru | IN |
| March Whle | Indianapolis | IN |
| Marhoeffer Packing | Muncie | IN |
| Marion County Building | Indianapolis | IN |
| Marion County General Hospital | Indianapolis | IN |
| Marion County Jail | Indianapolis | IN |
| Marion High School | Marion | IN |
| Marion Light & Heating | Marion | IN |
| Marion Mall Iron Works | Marion | IN |
| Marion Paper | Marion | IN |
| Marmon Motor | Indianapolis | IN |
| Marmon & Parry | Indianapolis | IN |
| Martinsville Gas & Electric | Martinsville | IN |
| Martinsville Light, Heat, Power & Water | Martinsville | IN |
| Martinsville Water Works | Martinsville | IN |
| Masonic Temple | Fort Wayne | IN |
| Masonic Temple | Goshen | IN |
| Maumee Collieries | Jasonville | IN |
| Maumee Collieries | Terre Haute | IN |
