| Arketex Ceramic | Brazil | IN |
| Arkla Air Conditioning | Evansville | IN |
| ARMCO | Muncie | IN |
| Armour & Company | Washington | IN |
| Armstrong Cork & Insulation | Dunkirk | IN |
| Arno Tape | Michigan City | IN |
| Arsenal Technical School | Indianapolis | IN |
| Art Center | Indianapolis | IN |
| Arvin Industries | Columbus | IN |
| Asbestos Covering & Roofing | Indianapolis | IN |
| Asbestos & Magnesia | Burns Harbor | IN |
| Asbestos Manufacturing | Huntington | IN |
| Associated Investment Addition | South Bend | IN |
| Associated Masonic Trustees | Fort Wayne | IN |
| Associates Invest Building | South Bend | IN |
| Atlantic Richfield | East Chicago | IN |
| Atlantic Richfield | Whiting | IN |
| Atlantic Richfield | Evansville | IN |
| Atlas Mutual Life Insurance | Indianapolis | IN |
| Atlas Underwear | Richmond | IN |
| Atomic Energy Commission | Newport | IN |
| Attica Electric & Power | Attica | IN |
| Atz Ice Cream Shop | Fort Wayne | IN |
| Auburn Foundry | Auburn | IN |
| Auburn Mining | Auburn | IN |
| Auburn Water | Auburn | IN |
| Auditer Of State | Indianapolis | IN |
| Aurora Casket | Aurora | IN |
| Austenal | La Porte | IN |
| Auto-Lite Battery | Vincennes | IN |
| Auto Wheel Service | Portland | IN |
| Avco | Richmond | IN |
| Avco | Connersville | IN |
| Avionics Building | South Bend | IN |
| Avon High School | Avon | IN |
| Babcock & Wilcox | Lawrenceburg | IN |
| Babcock & Wilcox | Hammond | IN |
| Babcock & Wilcox | Mount Vernon | IN |
| Badall | Hammond | IN |
| Baker McHenry & Welch | Evansville | IN |
| Baker McHenry & Welch | Kokomo | IN |
| Baker Specialty & Supply | Logansport | IN |
| Baldus | Fort Wayne | IN |
| Ball Brothers | Muncie | IN |
| Ball Memorial Hospital | Muncie | IN |
| Ball State Teachers College | Muncie | IN |
| Ball State University | Muncie | IN |
| Baltimore & Ohio Railroad | Garrett | IN |
| Baltimore & Ohio Railroad | Washington | IN |
| Banner Cement | Sellersburg | IN |
