| Company | Type | Founded |
|---|---|---|
| Avalon Hill | tabletop role-playing game publisher, board game publishing company | 1958 |
| Baltimore and Ohio Railroad | railway company, business | 1827 |
| Constellation Energy | public company | 1999 |
| Johns Hopkins University | private not-for-profit educational institution, research institute, open-access publisher, private university | 1876 |
| Laureate Education | international university, open-access publisher, education company, public company | 1998 |
| Peabody Institute | conservatory, school | 1857 |
| University System of Maryland | state university system | 1988 |