Plymouth County was formed 02-Jun-1685 when Plymouth Colony was divided into three counties: Plymouth, Bristol and Barnstable.
The Wampanoag Indians under sachem Massasoit (or Ousamequin) were living in this area when the earliest Europeans arrived. Other tribes to the west were the Narragansett, Nipmuck, Niantic, Saconnet, Massachuset, Mohegan, and Pequot.
On 21 November 1620 the Mayflower and its 102 passengers landed at what is now Plymouth. The Fortune arrived in November 1621. The Anne and Little James followed. By 1624 there were about 180 Europeans living in the Plymouth area.