Authorized on 9 April 1796, when the western portion of Tennessee County became part of the new state of Tennessee. The county was named for John Montgomery who was a soldier in the American Revolutionary War and an early settler who founded the city of Clarksville. When Montgomery County was formed, it was combined with land taken from Sumner County to form Robertson County. Later acts of the Tennessee General Assembly had further reduced Montgomery County by 1871 to its current size and boundaries. The county today has a total area of 544 square miles and a population count of 208,993 residents.