- Laboratories Dental, Port Jefferson Station
- Laboratories Medical, Port Jefferson Station
- Land Surveyor, Port Jefferson Station - Land Surveying Services
- Landscape Contractors & Designers, Port Jefferson Station
- Landscaping, Port Jefferson Station
- Landscaping Materials & Supplies, Port Jefferson Station
- Language Schools, Port Jefferson Station
- Laundry Self Service, Port Jefferson Station
- Lawn & Garden Equipment & Supplies, Port Jefferson Station
- Lawn & Garden Sprinkler Systems, Port Jefferson Station
- Lawn & Garden Supplies & Equipment, Port Jefferson Station
- Lawn Mowers & Power Equipment, Port Jefferson Station
- Lawyers & Attorneys, Port Jefferson Station
- Legal Professionals, Port Jefferson Station
|
- Libraries, Port Jefferson Station
- Life Insurance, Port Jefferson Station
- Limousine Service, Port Jefferson Station
- Linen Supply Services, Port Jefferson Station
- Liquor Stores, Port Jefferson Station
- Locks, Port Jefferson Station
- Locksmiths, Port Jefferson Station - Residence, Commercial, Safe & Auto Car Locksmith
- Locksmiths Equipment & Supplies, Port Jefferson Station
- Lodging, Port Jefferson Station
- Lodging Services, Port Jefferson Station
- Long Haul Trucking Companies, Port Jefferson Station
- Lumber & Lumber Products, Port Jefferson Station
- Lumber & Lumber Products, Port Jefferson Station
- Lutheran Church, Port Jefferson Station
|