Colonel Richard Nicolls, an English military officer, had conquered the territory that is now the states of New Jersey and New York when he forced the Dutch surrender of the New Netherland colony at the onset of the Second Anglo-Dutch War in 1664.
Twelve men, most of whom were Quakers from Long Island, purchased a tract that extended from Sandy Hook to the mouth of the Raritan River, upstream approximately 25 miles (40 km), and then southeast to Barnegat Bay.
[2][3] It was first known as Navesink, likely after a band of the Lenape who inhabited the area, and it was established into the settlements of Freehold, Middletown and Shrewsbury, and later as into Monmouth County.
[4] In 1675, Monmouth was established as one of the first four counties in the proprietary East Jersey colony, along with Bergen, Essex and Middlesex.
Other suggestions include that it was named for James Scott, 1st Duke of Monmouth (1649–1685), who had many allies among the East Jersey leadership.