There is one place named Extension in America.
All places in the world called "Extension".
Riverside (46)
Centerville (43)
Fairview (40)
Midway (39)
Franklin (39)
Union (37)
Greenwood (37)
Marion (36)
Glendale (36)
Salem (36)
Georgetown (35)
Oakland (35)
Liberty (35)
Fairfield (35)
Lincoln (35)
Pleasant Valley (35)
Florence (34)
Arlington (34)
Greenville (34)
Bethel (34)
Springfield (34)
Clinton (34)
Chester (33)
Kingston (33)
Clifton (33)
Milton (33)
Hamilton (33)
Newport (33)
Farmington (33)
Mount Pleasant (32)