1850 Atlas
| Name | What | Place | Pop | Other |
| Mecca | PT | Trumbull Co, OH | 872 | |
| Mechanic | T | Holmes Co, OH | 1,647 | |
| Mechanic's Falls | PV | Cumberland Co, ME | ||
| Mechanic's Grove | PO | Lancaster Co, PA | ||
| Mechanicsburgh | PO | Lehigh Co, PA | ||
| Mechanicsburgh | PV | Sangamon Co, IL | ||
| Mechanicsburgh | PV | Goshen twp, Champaign Co, OH | 682 | water by Little Darby creek |
| Mechanicsburgh | PV | Giles Co, VA | ||
| Mechanicsburgh | PO | Henry Co, IN | ||
| Mechanicsburgh | PB | Cumberland Co, PA | ||
| Mechanicstown | PV | Frederick Co, MD | ||
| Mechanicstown | PV | Fox twp, Carroll Co, OH | ||
| Mechanicsville | PV | Rutland Co, VT | ||
| Mechanicsville | PV | Stillwater twp, Saratoga Co, NY | water by Hudson river | |
| Mechanicsville | PO | Bucks Co, PA | ||
| Mechanicsville | PV | Louisa Co, VA | ||
| Mechanicsville | V | Sumter dist, SC | ||
| Mechanicsville | PV | Jasper Co, GA | ||
| Mechanicsville | PV | Cannon Co, TN | ||
| Mechanicsville | PO | Russell Co, AL | ||
| Mechisses | T | Washington Co, ME | 1,590 | water by East Machias river |
| Mechum's River | PO | Albemarle Co, VA | ||
| Mecklenburgh | PV | Hector twp, Tompkins Co, NY | ||
| Mecklenburgh | PV | Knox Co, TN | water by Holston river | |
| Medary | PO | Putnam Co, OH | ||
| Medfield | PT | Norfolk Co, MA | 966 | water by Charles & Stop rivers |
| Medford | PT | Middlesex Co, MA | 3,749 | water by Mystic river at head of navigation |
| Medford | PV | Evesham twp, Burlington Co, NJ | 3,022 | |
| Medina | PV | Ridgeway twp, Orleans Co, NY | water by Oak Orchard creek & Erie canal | |
| Medina | PT, CH | Medina Co, OH | 2,291 | seat of justice |
| Medina | PT | Lenawee Co, MI | 1,600 | |
| Medina | PO | Winnebago Co, IL | ||
| Medon | PO | Madison Co, TN | ||
| Medusa | PO | Albany Co, NY | ||
| Medway | PT | Norfolk Co, MS | 2,778 | water by Charles river |
| Medway | V | Liberty Co, GA | ||
| Medway | PO | Clark Co, OH | ||
| Medway | PO | Greene Co, NY | ||
| Medybemps | PO | Washington Co, ME | ||
| Meek's Hill | PO | York dist, SC | ||
| Meeme | PO | Manitoowoc Co, WI | ||
| Meeting Street | PO | Edgefield dist, SC | ||
| Meehoopany | PO | Luzerne Co, PA | ||
| Meigs | T | Adams Co, OH | 1,438 | |
| Meigs | T | Muskingum Co, OH | 1,512 | |
| Meigs Creek | PO | Morgan Co, OH | ||
| Meigsville | PT | Morgan Co, OH | 1,680 | |
| Meigsville | PV | Jackson Co, TN | water by Cumberland river | |
| Melendez Mills | PV, CH | Benton Co, FL | seat of justice | |
| Mellonville | PV | Claverack twp, Columbia Co, NY | ||
| Mellonville | PV, CH | Orange Co, FL | seat of justice | |
| Melmore | PV | Eden twp, Seneca Co, OH | water by Honey creek | |
| Melon | PO | Harrison Co, VA | ||
| Melpine | PO | Muscatine Co, IA | ||
| Melrose | PV | Clark Co, IL | 672 | |
| Melrose | V | Westfarms twp, Westchester Co, NY | ||
| Melrose | PO | Rockingham Co, VA | ||
| Melrose | PO | Middlesex Co, MA | ||
| Melrose | PO | Rush Co, IN | ||
| Melrose | PO | Nacogdoches Co, TX | ||
| Melton's | PO | Navarro Co, TX | ||
| Meltonsville | PV | Anson Co, NC | ||
| Meltonsville | PV | Marshall Co, AL | ||
| Melville | PO | Orange Co, NC | ||
| Melville | PO | Chattooga Co, GA | ||
| Melvin | PO | Ballard Co, KY | ||
| Melvin Village | PV | Carroll Co, NH | ||
| Memphis | PV, CH | Shelby Co, TN | 8,841 | seat of justice, water by Mississipi river |
| Memphis | PV | Scotland Co, MO | ||
| Memphis | PO | Pickens Co, AL | ||
| Memphis | PO | St Clair Co, MI | ||
| Menallen | PT | Adams Co, PA | 1,455 | |
| Menallen | T | Fayette Co, PA | 1,411 | |
| Menasha | PO | Winnebago Co, WI | ||
| Menasses' Gap | PO | Warren Co, VA | ||
| Mendam | PT | Morris Co, NJ | 1,720 | water by tributaries of Raritan & Whippany rivers |
| Mendon | PT | Rutland Co, VT | 504 | water by tributaries of Otter creek |
| Mendon | PT | Worcester Co, MA | 1,300 | water by Mill & Blackstone rivers |
| Mendon | PT | Monroe Co, NY | 3,351 | water by Honeyoye & Irondequoit creeks |
| Mendon | PO | Mercer Co, OH | ||
| Mendon | PO | Lenawee Co, MI | ||
| Mendon | PV | Adams Co, IL | ||
| Mendon | PO | Madison Co, IN | ||
| Menels | PO | Madison Co, KY | ||
| Menominee | T | Waukesha Co, WI | ||
| Menominee Falls | PO | Waukesha Co, WI | ||
| Menter | PO | Sheboygan Co, WI | ||
| Mentor | PT | Lake Co, OH | 1,571 | water by Lake Erie |
| Mentz | T | Cayuga Co, NY | 5,239 | water by Seneca river, Owasco inlet & Erie canal |
| Mequon River | PO | Washington Co, WI | ||
| Mequanego | T | Waukesha Co, WI | ||
| Merata | PO | Jefferson Co, PA | ||
| Mercer | PT | Somerset Co, ME | 1,186 | water by Sandy river |
| Mercer | PB, CH | Mercer Co, PA | 1,004 | seat of justice |
| Mercer | T | Butler Co, PA | 1,296 | |
| Mercer Salt Works | PO | Mercer Co, VA | ||
| Mercersburgh | PB | Montgomery twp, Franklin Co, PA | water by tributary of Conecocheague creek, seat of Marshall college | |
| Merchant's Bluff | PO | Darlington dist, SC |