- Laboratories Medical, Northport
- Landscape Contractors & Designers, Northport
- Landscaping, Northport
- Lawn & Garden Services, Northport
- Lawn Maintenance Services, Northport
- Lawyers & Attorneys, Northport
- Leather Goods Cleaners & Dyers, Northport
- Legal & Tax Services, Northport
- Legal Professionals, Northport
- Libraries, Northport
- Life Insurance, Northport
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- Lighting Consultants & Designers, Northport
- Liquor Stores, Northport
- Live Theaters, Northport
- Livestock, Northport
- Livestock Dealers, Northport
- Locks, Northport
- Locksmiths, Northport - Residence, Commercial, Safe & Auto Car Locksmith
- Locksmiths Equipment & Supplies, Northport
- Lodging, Northport
- Lutheran Church, Northport
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