| Southern Railway 1643 | |
| Powertype: | Steam |
| Serialnumber: | 37672 |
| Builddate: | September 1905 |
| Whytetype: | 0-6-0 |
| Driverdiameter: | 503NaN3 |
| Fueltype: | Coal |
| Firearea: | 29square feet |
| Boilerpressure: | 1852NaN2 |
| Cylindercount: | Two, outside |
| Cylindersize: | 20x |
| Tractiveeffort: | 32710abbr=onNaNabbr=on |
| Valvegear: | Stephenson |
| Operator: | Southern Railway Morehead and North Fork Railroad |
| Operatorclass: | A-7 |
| Fleetnumbers: | 1643 (SOU) 12 (M&NF) |
| Retiredate: | 1963 |
| Restoredate: | July 16, 2018 |
| Currentowner: | Age of Steam Roundhouse |
| Disposition: | Operational, based in Sugarcreek, Ohio |
Southern Railway 1643 is a preserved A-7 class 0-6-0 "Switcher" type steam locomotive built in 1905 by the Pittsburgh Works of the American Locomotive Company for the Southern Railway.
In 1952, the locomotive was sold to the Morehead and North Fork Railroad in Morehead, Kentucky. Renumbered 12, the locomotive operated on the Morehead line, until the company dieselized on April 1, 1963.[1] After the locomotive was retired, it was put into storage in one of the road's engine sheds. In 2011, No. 12 was purchased by Jerry Jacobson, who moved it to his Age of Steam Roundhouse building in Sugarcreek, Ohio. The locomotive was restored to operating condition in 2018, and it moved under steam for the first time in the 21st century on July 16.[2]