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How the Irish population in Mass. ranks against other states

Massachusetts has three of the most Irish counties in the country.

Boston's 2022 St. Patrick's Day parade. AP Photo/Steven Senne

March 27, 2022

There’s a good reason Boston is one of the best places to celebrate St. Patrick’s Day in the country. U.S. Census data confirms that Massachusetts is, in fact, one of the most Irish states.

Among its population, 19.8% claim Irish ancestry, which is about double the national population percentage of 9.7%. This means that about 1 in 5 people you meet in the Bay State have Irish ancestors.

What may surprise you is that the percentage of Massachusetts residents claiming Irish ancestry comes in second to a neighboring state.

New Hampshire takes home the gold with a population that is 20.2% Irish.

In fact, the top five states with the highest percentage of Irish ancestry among its citizens are all New England states. After New Hampshire and Massachusetts comes Rhode Island, at 17.6%, Vermont, at 17%, and Maine, at 16.6%.

But Massachusetts has other accolades when it comes to a large number of Irish descendants.

This map shows the percentage of people claiming Irish descent in each county in Massachusetts. *– U.S. Census Bureau*

While the states with the highest number of Irish descendants are simply the most populous states — California, Texas, New York, Florida, and Pennsylvania — despite being only the 16th most populous state, Massachusetts has one of the top 10 counties with the highest raw number of Irish descendants.

Middlesex County has the fourth-highest number of Irish descendants in it, at 310,458. It also has the highest percentage of Irish descendants in the top 10 list of counties with the most Irish descendants, at 19.4%.

But beyond that, three of the top 10 counties with the highest percentage of people claiming Irish ancestry are in Massachusetts. In fact, Plymouth County has the second-highest percentage of Irish descendants in the country, at 30.1%.

The county is second only to Cape May County in New Jersey, which just beats out Plymouth County with a percentage of Irish descendants at 30.2%.

Barnstable County also makes the list, coming in fourth with a percentage of Irish descendants at 26.5%, as does Norfolk County, coming in sixth with 25.6%.

According to a 2009 CUNY article on Irish immigration, the largest migration of Irish people to Massachusetts happened in the 1840s and 1850s. Dire economic conditions, especially the potato famine of 1845, led Irish immigrants to seek a new life in the U.S.

Many of the descendants of those immigrants are still in the state today. In fact, the most common last name in Massachusetts is Sullivan, a very Irish last name.