| Name | Phone | Category |
| L/B Water Service, Inc. | (301) 682-9580 | Distributors/Wholesalers |
| LabCorp | 301-481-9593 | Medical |
| LaBella Medispa | 301-829-4115 | Spa |
| Ladiant, Inc. dba Jerry's Subs & Pizza | 703-851-6179 | Restaurants/Cafes |
| Landmark Insurance & Financial Group | 443-470-8009 | Human Resources |
| Law Office of John C. Hanrahan, LLC | 301-620-4378 | Attorneys |
| Lazy Daze Cleaning Service | 301-874-2023 | Cleaning/Janitorial |
| Leadership Frederick County | 301-676-1147 | Associations |
| Leadership Techniques LLC | 301-667-3915 | Training/Coaching |
| Leiters' Fine Catering, Inc. | (301) 223-7070 | Caterers |
| Liberty Mutual Group | (301) 620-1061 | Insurance Agencies/ Brokers |
| Life Technologies | (240) 379-4159 | Biomedical/ Biotechnology |
| Life Wellspring | (301) 371-7460 | Training/Coaching |
| Lincoln Financial Advisors | 443-982-2660 | Investment Management |
| Linton Shafer Warfield & Garrett, P.A. | (301) 662-9200 | Accountants/CPA's |
| Lipinski Chiropractic PA | 301-620-7111 | Chiropractor |
| Little Sparkie Electric, LLC | (301) 606-5181 | Electrical Contractors |
| The Lodges at Gettysburg | 717 814 9894 | Lodging/Hotels & Motels |
| Logo Wear Direct | (301) 606-7000 | Embroidery |
| Longhorn Steakhouse | 301-525-6907 | Restaurants/Cafes |
| Lonza Walkersville, Inc. | (301) 898-7025 | Biomedical/ Biotechnology |
| Lough Memorials | (301) 663-3441 | Funerals/Cemeteries |
| Love & Company | (301) 663-1239 | Advertising |
| Lucas Racing, Inc. | (301) 865-7123 | Farm |