Forsyth County was created in 1832 from parts of the original Cherokee Country. It was named for John Forsyth, Governor of Georgia from 1827-1829 and Secretary of State under Presidents Andrew Jackson and Martin Van Buren.

Much of the eastern side of the county lies on the shores of Lake Sidney Lanier, one of the busiest recreational bodies of water in the nation with 200 miles of shoreline. Created in the 1950s with the impoundment of the Chattahoochee River at Buford Dam, the lake has accelerated the growth of the county, as well as provided recreational enjoyment for many throughout north Georgia. The lake is home to Southern Bald Eagles and Peregrine Falcons, both endangered species.

Forsyth County has been ranked by the U.S. Census as the fastest growing county in Georgia.