Franklin County is a county in the U.S. state of Massachusetts. As of the 2010 census, the population was 71,372, that makes it the least-populous county on the Massachusetts mainland, and the third-least populous county in the state. The county seat and most populous city is Greenfield. The largest town by area is New Salem.
Franklin County was created on June 24, 1811 from the northern third of Hampshire County. It was named for Benjamin Franklin.