- Machine Shop & Tool Repair Service, Barrington
- Machinery, Supplies & Equipment - Business Supplies Related, Barrington
- Machinery, Supplies & Equipment - Construction & Contractor Related, Barrington
- Management Consultants & Services, Barrington
- Manicurists & Pedicurists, Barrington
- Manufacturing, Barrington
- Manufacturing Products, Barrington
- Marriage & Family Counselors, Barrington
- Mechanical Contractors, Barrington - Install, Service & Repair
- Medical & Dental Management, Barrington
- Medical Management & Business Administration Service, Barrington
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- Medical Supplies & Equipment, Barrington
- Membership Sports & Recreation Clubs, Barrington
- Mental Health Specialists, Barrington - Psychologist, Psychiatrist, Psychotherapist, etc
- Merchandise Sales Events, Barrington
- Miscellaneous Household Item Repair, Barrington
- Miscellaneous Government, Barrington
- Miscellaneous Professional, Barrington
- Monuments, Tombstones, Markers & Memorials, Barrington
- Motor Vehicle, Barrington
- Moving Companies, Barrington
- Music, Barrington
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