2000
#1,240
National surname rank
Recorded bearers 26,011
First available Census row
Per 100,000 9.64
Uncommon Last name
Cassidy
An Anglicized form of an Irish patronymic surname meaning "descendant of Caiside," derived from an Irish nickname meaning "curly-haired."
According to the 2020 US Census Bureau surname tables, roughly 29,251 Americans carry the last name Cassidy. That puts it at #1,347 in the national surname ranking, appearing at a frequency of 8.53 per 100,000 people (about 1 in 11,718 residents).
This page is the full Name Census profile for the Cassidy surname. You will find the Census Bureau frequency data, a multi-census history view, an ancestry and ethnicity breakdown based on self-reported demographics, the name's meaning and origin where available, and answers to the most common questions people ask about this surname.
For British records, Name Census UK has a British surname profile for Cassidy with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
29K
1 in 11,718
Census rank
#1,347
2020 decennial data
Per 100,000
8.5
Frequency rate
Recorded bearers
26K
uncommon in the US
Popularity narrative
The Census Bureau recorded 25,508 bearers of the surname Cassidy in its 2020 decennial surname file. At a rate of 8.53 per 100,000 residents, it holds the 1347th position in the national surname ranking.
Among Census respondents with the surname Cassidy, the largest self-reported group is White at 89.9%. The next largest groups are Hispanic (3.8%) and Two or More Races (3.2%).
Origin
Meaning and origin of Cassidy
The surname Cassidy is an anglicized form of the Irish Gaelic name O'Caiside. It originated in Ireland during the 11th century, primarily in County Fermanagh. The name is derived from the Gaelic personal name Caiside, which means "curly-headed" or "curly-haired."
O'Caiside was an important Irish clan, known for their involvement in the Irish Confederate Wars of the 17th century. The name can be found in various ancient Irish manuscripts and records, including the Annals of the Four Masters, which document the history of Ireland from the earliest times to the 17th century.
One of the earliest recorded instances of the surname Cassidy dates back to the 13th century, when a man named Gillebertus O'Caiside was mentioned in the Annals of Ulster in 1261. The name was also found in the Fiants of the Tudor Sovereigns, a collection of records from the reigns of Henry VIII, Edward VI, and Mary I.
The Cassidy surname has been associated with several notable individuals throughout history. One of the earliest was Sir Thomas Cassidy (c. 1570-1651), an Irish soldier and landowner who fought for the English Crown during the Irish Confederate Wars. Another prominent figure was Patrick Cassidy (1756-1828), an Irish rebel leader who participated in the Irish Rebellion of 1798.
In the 19th century, John Cassidy (1809-1865) was a prominent Irish-American businessman and politician who served as the 84th Mayor of New York City from 1858 to 1859. William Cassidy (1815-1873) was an Irish-American prelate who served as the Bishop of Brooklyn from 1853 until his death.
More recently, Brendan Cassidy (1924-2016) was an Irish Jesuit priest, theologian, and author, known for his work on Thomas Aquinas and Catholic social teaching. Shaun Cassidy (born 1958) is an American actor, writer, and producer, best known for his roles in the 1970s television series "The Hardy Boys" and "The Hardy Boys/Nancy Drew Mysteries."
Demographics
Ancestry and ethnicity for Cassidy
Among Census respondents with the surname Cassidy, the largest self-reported group is White at 89.9%. The next largest groups are Hispanic (3.8%) and Two or More Races (3.2%).
The bar chart below shows how Cassidy bearers described their own race and ethnicity on the 2020 Census form. The Census Bureau groups responses into six broad categories: White, Black or African American, Hispanic or Latino, Asian and Pacific Islander, American Indian and Alaska Native, and Two or More Races. When a category has too few respondents for a given surname, the Bureau suppresses the figure to protect individual privacy, which is why some names show fewer than six slices.
Percentages are shown for every Census year so the breakdown stays comparable over time. When the source file also includes raw headcounts, Name Census shows those alongside the percentages in the legend.
Keep in mind that these are self-reported numbers. A person's surname does not determine their race or ethnicity, and the distribution you see here reflects the specific population who happened to carry the Cassidy surname at the time of the 2020 Census, not any inherent property of the name itself.
- White89.9% · 22,925
- Hispanic or Latino3.8% · 959
- Two or more races3.2% · 819
- Black or African American2.0% · 506
- Asian and Pacific Islander0.9% · 223
- American Indian and Alaska Native0.3% · 76
Timeline
Historical Census data for Cassidy
Cassidy appears in 3 published Census surname files: 2000, 2010, 2020. The cards below show how the name's rank and bearer count changed across each release.
2010
#1,325
National surname rank
Recorded bearers 26,590
+579 bearers (+2.2%)
Per 100,000 9.01
Rank movement Down 85 places
2020
#1,347
National surname rank
Recorded bearers 25,508
-1,082 bearers (-4.1%)
Per 100,000 8.53
Rank movement Down 22 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #1,240 | 26,011 | 9.64 | First available Census row | First available Census row |
| 2010 | #1,325 | 26,590 | 9.01 | +579 bearers (+2.2%) | Down 85 places |
| 2020 | #1,347 | 25,508 | 8.53 | -1,082 bearers (-4.1%) | Down 22 places |
For 2020, the Census Bureau published race and Hispanic-origin columns as counts rather than percentages. Name Census converts those counts back into shares so the ancestry section stays comparable with the older surname files.
Year on year
2010 vs 2020 Census
How has the Cassidy surname changed between Census years? The chart shows bearer count side by side, and the table compares rank, count, and frequency.
Census year comparison
20102020
| Metric | 2010 | 2020 | Change |
|---|---|---|---|
| Rank | #1,325 | #1,347 | -1.7% |
| Count | 26,590 | 25,508 | -4.1% |
| Per 100K | 9.01 | 8.53 | -5.3% |
Between the 2010 and 2020 Census, the number of Cassidy bearers went from 26,590 to 25,508 (-4.1% change). The surname moved down 22 positions in the national ranking, going from #1,325 to #1,347.
Notable bearers
Famous people with the surname Cassidy
FAQ
Cassidy surname: questions and answers
How many people in the U.S. have the surname Cassidy?
Name Census estimates that about 29,251 living Americans carry the surname Cassidy. Using the current population baseline, that works out to roughly 1 in 11,718 residents.
How common is Cassidy?
Cassidy ranks #1,347 in the 2020 Census surname tables and is classified on this site as "Uncommon." The Census recorded the name at a frequency of 8.53 per 100,000 residents, which is about 9 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 25,508 people with the surname Cassidy. That is different from the site's living-bearer estimate (29,251), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 8.53 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 8.53 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 9 of them to have the surname Cassidy.
Has Cassidy become more or less common over time?
Between 2010 and 2020, the surname Cassidy went from 26,590 recorded bearers to 25,508. That is a decrease of 1,082 (-4.1%). In the national ranking it fell from #1,325 to #1,347.
What does the Census say about the background of Cassidy?
Among Census respondents with the surname Cassidy, the largest self-reported group is White at 89.9%. The next largest groups are Hispanic (3.8%) and Two or More Races (3.2%). These figures come from the 2020 Census Bureau surname tables, based on how respondents described their own race and ethnicity.
Which group reports this surname most often?
White is the largest self-reported group for the surname Cassidy in the 2020 Census, accounting for 89.9% (22,925 people in the source table).
What is the full ancestry breakdown?
Cassidy appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (89.9%), Hispanic (3.8%), Two or More Races (3.2%). For 2020, the source file also published raw headcounts for each group, which is why this page can show both percentages and counts in the ancestry section.
Is this page using the latest Census data?
Yes. This page is using the latest surname file currently loaded on Name Census, which is 2020. The historical section above also keeps any older Census surname entries we have for Cassidy (2000, 2010, 2020).
Does the Census include every surname?
No. The Census Bureau only publishes surnames that appeared at least 100 times in a given decennial Census. That means very rare surnames are excluded entirely, and a surname can appear in one Census release but disappear from a later one if it falls below the reporting threshold.
Why don't the ancestry percentages always add up to exactly 100%?
There are two main reasons: rounding and suppression. The Census Bureau rounds published values, and it may suppress very small cells to protect privacy. For 2020, the Bureau also published raw group counts rather than direct percentages, so Name Census converts those counts back into shares for comparability across census years.
What does Cassidy mean?
An Anglicized form of an Irish patronymic surname meaning "descendant of Caiside," derived from an Irish nickname meaning "curly-haired." The fuller origin note on this page goes into more detail.
Where does the surname data come from?
All surname statistics on Name Census are drawn from the US Census Bureau's decennial surname frequency tables. These files list every surname that appeared 100 or more times in the 2020 Census, along with a count, a per-100,000 rate, and a self-reported demographic breakdown. You can read the full explanation on our methodology page.
How does Name Census estimate living bearers?
For surnames, Name Census does not age cohorts the way it does for first names. Instead, it takes the Census Bureau's published frequency for Cassidy (8.53 per 100,000) and applies that rate to the current U.S. resident population to estimate how many living Americans have the surname today.
How many people have the surname Cassidy?
HowManyOfMe.org, our sister site, answers that with the living-bearer count in one glance.