- Labor Organizations, Beltsville
- Laboratories Medical, Beltsville
- Laboratory Equipment Repair & Service, Beltsville
- Land Surveyor, Beltsville - Land Surveying Services
- Landscape Contractors & Designers, Beltsville
- Landscaping, Beltsville
- Laser Equipment Repair & Service, Beltsville
- Late Night Restaurants, Beltsville
- Laundry & Dry Cleaning Equipment & Supplies, Beltsville - Cleaners & Dryers Sales, Repair, Service & Leasing
- Lawn & Garden Equipment & Supplies, Beltsville
- Lawn & Garden Services, Beltsville
- Lawn & Garden Sprinkler Systems, Beltsville
- Lawn & Tree Service, Beltsville
- Lawn Maintenance Services, Beltsville
- Lawyers & Attorneys, Beltsville
- Legal & Tax Services, Beltsville
- Legal Professionals, Beltsville
- Letter Shop & Addressing Services, Beltsville
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- Life Insurance, Beltsville
- Lighting Consultants & Designers, Beltsville
- Lighting Fixtures & Equipment, Beltsville
- Lighting Fixtures Repair, Maintenance & Installation, Beltsville
- Limousine Service, Beltsville
- Liquor Stores, Beltsville
- Lithographic Printing, Beltsville
- Live Theaters, Beltsville
- Loans Personal, Beltsville
- Locks, Beltsville
- Locksmiths, Beltsville - Residence, Commercial, Safe & Auto Car Locksmith
- Locksmiths Equipment & Supplies, Beltsville
- Lodging, Beltsville
- Lodging Services, Beltsville
- Long Haul Trucking Companies, Beltsville
- Lumber & Lumber Products, Beltsville
- Lumber & Lumber Products, Beltsville
- Lutheran Church, Beltsville
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