The seal was adopted by the Plymouth County Commissioners on March 31, 1931 under the authority of the General Laws, Chapter 34, Section 14, and was designed by Frederic T. Bailey of North Scituate who was, at that time and for many years, Chairman of the county commissioners.
The seal was designed to truly represent the County of Plymouth and it shows the Mayflower at rest after landing her passengers on Plymouth Rock in 1620. Her hull is reflected in the water as she swings at anchor in the quiet harbor; the cargo has been unloaded "on a stern and rockbound coast" a new nation has been born!
Around the Mayflower is a chaplet of pearls, twenty-seven in number, representing the municipalities now bound together in County government; each complete in itself but united in the score and more of government functions which are better carried on by the County. The value of the chaplet is in the value of its individual pearls, yet worth is not determined by size alone; the smallest being the Towns of Plympton and Rochester, and the largest being the City of Brockton.
The County of Plymouth was established on the second day of June in 1685 by the General Court of Plymouth Colony, then sitting at Plymouth.