| John H. Heald & Company | Baltimore | MD |
| John J McGraw | Baltimore | MD |
| John Laforge | Baltimore | MD |
| John L Deaton Center | Baltimore | MD |
| John Motley | Baltimore | MD |
| John Russell Pope | Baltimore | MD |
| Johns Boiler Service | Baltimore | MD |
| Johns Hopkins Hospital | Baltimore | MD |
| Johns Hopkins School Of Medicine | Baltimore | MD |
| Johns Hopkins University | Baltimore | MD |
| Johns Hopkins University | Laurel | MD |
| John Woolman | Baltimore | MD |
| Jose Artigas | Baltimore | MD |
| Jose Marti | Baltimore | MD |
| Joseph E. Seagram & Sons | Baltimore | MD |
| Joseph E. Seagram & Sons | Relay | MD |
| Joseph Feuer | Baltimore | MD |
| Joseph Leidy | Baltimore | MD |
| Joseph P. Bradley | Baltimore | MD |
| Joseph Seagram & Sons | Lansdowne | MD |
| Joseph Seagram & Sons | Baltimore | MD |
| Jose Warti | Baltimore | MD |
| Joshua W. Alexander | Baltimore | MD |
| Joyce Kilmer | Baltimore | MD |
| Jules Fribourg | Baltimore | MD |
| J Whitridge Williams | Baltimore | MD |
| Kaiser Aluminum & Chemical | Halethorpe | MD |
| Kaiser Aluminum & Chemical | Baltimore | MD |
| Kaspaugh Rubber | Baltimore | MD |
| Katina | Baltimore | MD |
| Kaydon Ring & Seal | Baltimore | MD |
| Kay Management | Silver Spring | MD |
| Keelung | Baltimore | MD |
| Kelly Springfield Tire & Rubber | Cumberland | MD |
| Kelvin & Hughes | Annapolis | MD |
| Kennecott Copper | Baltimore | MD |
| Kennecott Refining | Baltimore | MD |
| Keswick Home for the Incurables | Baltimore | MD |
| Ketcham Brothers | Baltimore | MD |
| Key Bridge Administration Building | Dundalk | MD |
| Key Highway Shipyard | Baltimore | MD |
| Keyser Building, Adams & Schwab | Baltimore | MD |
| Keystone State | Baltimore | MD |
| Kimball Tyler | Baltimore | MD |
| Kimmel & Kimmel | Gaithersburg | MD |
| Kingan & Company | Baltimore | MD |
| Klots Throwing | Cumberland | MD |
| Klots Throwing | Lonaconing | MD |
| Kopalnia Miechpwice | Baltimore | MD |
| Koppers | Baltimore | MD |
