| Phelps Dodge | Fort Wayne | IN |
| Philadelphia Quartz | Jeffersonville | IN |
| Philadelphia Quartz | Anderson | IN |
| Philco | Connersville | IN |
| Piel Brothers Starch | Indianapolis | IN |
| Pillsbury | Terre Haute | IN |
| Pillsbury | New Albany | IN |
| Pillsbury Farms | Orleans | IN |
| Pioneer Enterprises | Elberfeld | IN |
| Pioneer Hat Works | Wabash | IN |
| Pitman Moore | Indianapolis | IN |
| Pittsburgh Plate Glass | Shelbyville | IN |
| Pittsburgh Plate Glass | Elwood | IN |
| Pittsburgh Plate Glass | Kokomo | IN |
| Plax | Ligonier | IN |
| Pleasant Township School | Laketon | IN |
| Plibrico | Fort Wayne | IN |
| Plumbers Supply | Evansville | IN |
| Plumbing & Industrial Sup | Evansville | IN |
| Plymouth Fertilizer | Plymouth | IN |
| Plymouth Tube | Winamac | IN |
| Pneu Tech Rubber | Indianapolis | IN |
| Pope Foundry & Machine | Marion | IN |
| Portland Forge | Portland | IN |
| Powered Equipment | Terre Haute | IN |
| Power Equipment | Terre Haute | IN |
| Power Plant | Martinsville | IN |
| Power Plant | Fort Wayne | IN |
| Power Plant | New Albany | IN |
| Power Plant | Frankfort | IN |
| PPG Industries | Shelbyville | IN |
| PPG Industries | Kokomo | IN |
| Prarie Heights Junior High School | Lagrange | IN |
| Princeton Mining | Princeton | IN |
| P. R. Mallory | Indianapolis | IN |
| Pr Mallory & Company | Indianapolis | IN |
| Producers Dairy Marketing Association | Orleans | IN |
| Producers Marketing Association | Orleans | IN |
| Progress Laundry | Indianapolis | IN |
| Proof | Goshen | IN |
| Protestant Deaconess Hospital | Evansville | IN |
| Protofore Machine & Engineering | South Bend | IN |
| Prox & Bureet | Terre Haute | IN |
| Psi Energy | Terre Haute | IN |
| Psi Energy | Edwardsport | IN |
| Psi Energy | West Terre Haute | IN |
| Psi Energy | New Albany | IN |
| Pt Components | Indianapolis | IN |
| Public Ledger Building | Anderson | IN |
| Public Service Company Of Indiana | Terre Haute | IN |
