Plymouth County is part of the Boston–Cambridge–Newton, MA–NH Metropolitan Statistical Area.

There were 181,524 housing units at an average density of 275 per square mile (106/km2).

The leading ancestry group in Plymouth County is Irish, with 31%.

[14] In terms of ancestry, 33.7% were Irish, 15.8% were Italian, 15.3% were English, 7.3% were German, and 3.7% were American.

[18][19][20] Plymouth County is governed by three County Commissioners:[21] Chairman Jared L. Valanzola (R-Plymouth) [22] , Commissioner Sandra M. Wright (R-Bridgewater), and Commissioner Gregory M. Hanley (D-Abington) Other county elected officials include Sheriff Joseph D. McDonald, jr. (R-Kingston), District Attorney Timothy Cruz (R-Marshfield), Treasurer Thomas J. O'Brien (D-Plymouth), Register of Deeds John R. Buckley, jr. (D-Scituate), Register of Probate Matthew McDonough (D-Marshfield), and Clerk of Courts Robert Creedon (D-Brockton) From the late 19th to the mid 20th centuries, Plymouth County was a Republican Party stronghold in presidential elections.

From 1876 to 1988, only three Democrats carried the county: Lyndon Johnson, Hubert Humphrey, and Jimmy Carter.

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.

Radio stations located in Plymouth County include: The first radio broadcast in history was made in 1906, from the Brant Rock neighborhood in the town of Marshfield.

The Brockton Enterprise is the only daily newspaper published in the county, although the Quincy Patriot Ledger has extensive coverage of the South Shore of Massachusetts generally and Plymouth County in particular.

There are numerous weekly newspapers published in the county, including: Many were operated by the Memorial Press Group, based in Plymouth, until the chain was sold to GateHouse Media in 2006.