- Northern Oil Company1
- Northern Pacific Railway Company. Land Department1
- Nutter, Frank H., 1853-1932.1
- O'Hara and Zeese Civil engineers and Surveyors1
- Ogaard, Louis A.1
- Oliver Iron Mining Company (Duluth, Minn.). Mining Engineering Department.1
- Papike, J. J. (James Joseph), 1937-20201
- Parham, Wallace E.1
- Payne, C. M.1
- Pederson, R.1
- Pezolt, F.1
- Phillips Petroleum Company1
- Phinney, William C.1
- Piegat, James1
- Pope, John, 1822-18921
- Power, J. B. (James Buel), 1833-19121
- Ray, F. G.1
- Register Print (Warren, Minn.)1
- Reynolds, Wade K.1
- Rice & Bell1