| 21ST CENTURY INVESTMENT ADVISORS, INC. | D03000585 | 1990-04-23 | Merged | BOWIE |
| 21ST CENTURY JOSEPH VISION MOVEMENT, INC | D13261110 | 2009-10-09 | Suspended | CLARKSVILLE |
| 21ST CENTURY LAWN & LANDSCAPING, LLC | W13337704 | 2009-12-04 | Active | MOUNT AIRY |
| 21ST CENTURY LOBBYING, INC. | D07413594 | 2003-06-06 | Suspended | BETHESDA |
| 21ST CENTURY LTD. | F02768414 | 1989-04-03 | Suspended | BLOOMSBURG |
| 21ST CENTURY MANAGEMENT, INC. | D04535118 | 1996-11-04 | Suspended | UNION BRIDGE |
| 21ST CENTURY MARKETING CORPORATION | D04037313 | 1994-12-27 | Suspended | KENSINGTON |
| 21ST CENTURY MARKETING GROUP, LLC | Z13624028 | 2010-06-15 | Suspended | UPPER MONTCLAIR |
| 21ST CENTURY MARYLAND, INC | D21497375 | 2021-03-11 | Suspended | MARLBORO |
| 21ST CENTURY MEDIA CORP. | D03670023 | 1993-06-01 | Suspended | ELLICOTT CITY |
| 21ST CENTURY MEDIA NEWSPAPER, LLC | Z15442437 | 2013-09-11 | Suspended | WILMNGTON |
| 21ST CENTURY MEDIAWORKS, LLC | W18657627 | 2018-03-09 | Suspended | BALTIMORE |
| 21ST CENTURY MEDICAL SUPPLIES, INC | D17487133 | 2016-09-12 | Suspended | LARGO |
| 21ST CENTURY MORTGAGE CORPORATION | D04440822 | 1996-06-26 | Suspended | PRINCE FREDERICK |
| 21ST CENTURY MORTGAGE SERVICES, INC. | D03347648 | 1992-01-03 | Suspended | CLINTON |
| 21ST CENTURY MUSIC SOLUTIONS LLC | Z14472237 | 2011-11-30 | Suspended | — |
| 21ST CENTURY ONCOLOGY OF HARFORD COUNTY, MARYLAND L L C | W11292919 | 2006-05-15 | Dissolved | BEL CAMP |
| 21ST CENTURY ONCOLOGY SERVICES, INC | F14465165 | 2011-11-28 | Dissolved | WILMINGTON |
| 21ST CENTURY ONLINE PUBLISHING COMPANY, INC. | D04357620 | 1996-03-14 | Dissolved | WALDORF |
| 21ST CENTURY PAINTING COMPANY, INC. | D03352689 | 1992-01-09 | Suspended | GLEN BURNIE |
| 21ST CENTURY PARTNERS, INC. | D04575825 | 1996-12-27 | Suspended | BALTIMORE |
| 21ST CENTURY PHYSICIAN, INCORPORATED | D03901873 | 1994-05-31 | Suspended | BALTIMORE |
| 21ST CENTURY POWER SOLUTIONS, LLC | W12973012 | 2009-03-20 | Active | ELDERSBURG |
| 21ST CENTURY PRODUCTS, LLC | W18644286 | 2018-03-05 | Suspended | CHRUCHVILLE |
| 21ST CENTURY PROGRESSIVE TECHNOLOGIES, INC. | D04991568 | 1998-05-05 | Suspended | COLUMBIA |
| 21ST CENTURY PROPERTIES COMPANY LLLP | M04848735 | 1997-11-25 | Merged | COLUMBIA |
| 21ST CENTURY PROTECTION SERVICES, L.L.C | W15505837 | 2013-10-18 | Suspended | SILVER SPRING |
| 21ST CENTURY PUBLISHING, INC | D10637700 | 2005-05-18 | Suspended | SYKESVILLE |
| 21ST CENTURY PUBLISHING, INC. | D04495305 | 1996-09-12 | Suspended | ELLICOTT CITY |
| 21ST CENTURY QUALITY CARE LLC | W13697958 | 2010-08-09 | Suspended | LANHAM |
| 21ST CENTURY RENEWABLE SOLUTIONS LLC | W17500844 | 2016-09-19 | Suspended | BELTSVILLE |
| 21ST CENTURY SALES, LLC | Z14484984 | 2012-01-26 | Active | WILMINGTON |
| 21ST CENTURY SEAFOOD, INC. | D02947406 | 1990-01-26 | Suspended | — |
| 21ST CENTURY SECURITY, LLC | W12198321 | 2007-10-22 | Active | — |
| 21ST CENTURY SOFTWARE CORP. | D03664984 | 1993-05-28 | Suspended | SILVER SPRING |
| 21ST CENTURY SOFTWARE, INC | F14326482 | 2011-09-30 | Suspended | ASHBURN |
| 21ST CENTURY SOLUTIONS LLC | W06479232 | 2001-09-24 | Suspended | BALTIMORE |
| 21ST CENTURY SOLUTIONS, INC | D05863485 | 2000-06-28 | Dissolved | SILVER SPRING |
| 21ST CENTURY SOLUTIONS, L.L.C | W15536337 | 2013-11-08 | Suspended | BALTIMORE |
| 21ST CENTURY SPORTS GROUP LLC | W12722716 | 2008-09-19 | Suspended | RANDALLSTOWN |
| 21ST CENTURY STAFFING LLC | Z13919196 | 2010-12-21 | Suspended | BLUE BELL |
| 21ST CENTURY STRATEGIC INVESTMENTS, LTD., | D05382783 | 1999-06-24 | Suspended | GERMANTOWN |
| 21ST CENTURY SUNSHINE, INC. | D03905049 | 1994-06-08 | Suspended | ANNAPOLIS |
| 21ST CENTURY SYSTEMS AND SOFTWARE SOLUTIONS LLC | W15944622 | 2014-06-27 | Suspended | WHITE PLAINS |
| 21ST CENTURY TEACH USA, LLC | W21451489 | 2021-02-18 | Active | BELSTVILLE |
| 21ST CENTURY TECHNOLOGIES, INC. | D02805513 | 1989-05-31 | Suspended | ANNAPOLIS |
| 21ST CENTURY TECHNOLOGY SERVICES INC. | D06093504 | 2000-12-21 | Suspended | CLARKSVILLE |
| 21ST CENTURY THRESHOLD PROJECT, INC | D07777022 | 2004-01-30 | Dissolved | TOWSON |
| 21ST CENTURY TOWING INC | D13633318 | 2010-06-25 | Suspended | BELTSVILLE |
| 21ST CENTURY VIDEO PRODUCTION, LLC | W21981535 | 2021-07-12 | Active | SILVER SPRING |