How Common Is the Last Name Cassidy?
An estimated 29,251 people in the United States share the surname Cassidy. That's about 1 in 11,718 Americans. This data comes from the 2020 U.S. Census Bureau surname frequency tables.
This page covers the Cassidy surname's frequency in the U.S. population, its rank among all American surnames, and a breakdown of ancestry and ethnicity data from the Census. You can also check how many people share any first + last name combination involving Cassidy.
Estimated Americans with this Surname
29,251
About 1 in 11,718 people in the U.S.
Census Rank
#1,347
Frequency Rate
8.53
per 100,000 people
Census Count
25,508
2020 Census
Data Source
2020
U.S. Census Bureau
Ancestry and Ethnicity for Cassidy
The Cassidy surname is most commonly associated with people who identify as White (89.87%). The next largest groups are Hispanic (3.76%) and Two or More Races (3.21%).
Self-reported race and ethnicity from the 2020 U.S. Census Bureau surname tables. Some categories may be suppressed for privacy when sample sizes are small.
Historical Census Data for Cassidy
Cassidy appears in 3 published Census surname releases on this site (2000, 2010, 2020). From 2000 to 2020, the raw count became less common and the per-100,000 rate became less common. Its best published rank was #1,240 in 2000.
Between the 2010 and 2020 census releases, the surname Cassidy became less common in the United States. Both the raw count and the population-adjusted frequency moved down.
The line to watch most closely is per 100,000 people. That adjusts for overall population growth, so it shows whether Cassidy became a bigger or smaller share of the country, not just whether the raw count went up.
Census Count Over Time
Raw Census count in each published surname release.
25,508 to 26,590
Per 100,000 Over Time
Population-adjusted frequency, which is usually the cleaner trend line.
8.53 to 9.64
Release-by-release summary
Each row is a published Census surname table for Cassidy. The change column compares each release to the one before it.
| Year | Rank | Count | Per 100K | Change vs prior release | Largest recorded group |
|---|---|---|---|---|---|
| 2000 | #1,240 | 26,011 | 9.64 | Baseline release | White (93.86%) |
| 2010 | #1,325 | 26,590 | 9.01 |
Count 2.20%
Rate -6.76% | White (92.64%) |
| 2020 Latest | #1,347 | 25,508 | 8.53 |
Count -4.15%
Rate -5.43% | White (89.87%) |
If the raw count rose but the per-100,000 number fell, the surname still became less common relative to the size of the U.S. population. That is why the frequency rate usually tells the clearer story.
Recorded ancestry change
These percentages show how the Census profile for this surname shifted across the published surveys on this site.
| Ancestry | 2020 | 2010 | 2000 | Change Since 2000 |
|---|---|---|---|---|
| White | 89.87% | 92.64% | 93.86% | -4.34% |
| Black | 1.98% | 2.22% | 2.09% | -5.22% |
| Asian and Pacific Islander | 0.87% | 0.69% | 0.50% | 54.46% |
| American Indian and Alaska Native | 0.30% | 0.39% | 0.36% | -18.86% |
| Two or More Races | 3.21% | 1.41% | 1.31% | 84.09% |
| Hispanic | 3.76% | 2.66% | 1.88% | 66.66% |
These percentages come from self-reported Census data. They describe how the recorded makeup of people using the surname Cassidy changed from 2000 through 2020, not the deeper family origin of every bearer of the name.
First Name + Cassidy Combinations
How many people share a full name with Cassidy as the last name? Click a combination below to see the estimate, or search any pairing.
Cassidy Surname: Questions and Answers
How common is the last name Cassidy?
Cassidy is the #1,347 most common surname in the United States, with an estimated 29,251 people sharing this last name. It appears at a rate of 8.53 per 100,000 Americans.
Has the surname Cassidy become more or less common over time?
In the published Census surname tables on this site, Cassidy moved from 26,011 people in 2000 to 25,508 in 2020. The more important line is the population-adjusted rate, which changed from 9.64 to 8.53 per 100,000.
Why can the raw count go up while the rate per 100,000 goes down?
Because the total U.S. population can grow faster than the surname itself. A surname can have more people in absolute numbers but still make up a smaller share of the country, which is why the per-100,000 figure often tells the clearer story.
What does the ancestry change table show for Cassidy?
It compares the published Census demographic mix for Cassidy across releases on this page. That helps you see whether the recorded share of the surname shifted between groups over time, but it still does not tell the full family history of every person with the name.
What does 8.53 per 100,000 mean?
It means that if you picked 100,000 people in the United States at random, about 8.53 of them would have the surname Cassidy. This is usually the clearest way to compare surnames because it adjusts for the size of the total population.
What ethnicity is the surname Cassidy?
The Cassidy surname is most commonly associated with people who identify as White (89.87%). The next largest groups are Hispanic (3.76%) and Two or More Races (3.21%). This data comes from the 2020 U.S. Census Bureau surname tables, which include self-reported race and ethnicity breakdowns.
Does the ancestry table tell the exact family origin of everyone named Cassidy?
No. It shows how people with the surname Cassidy identified in the Census. That is useful context, but it does not prove the deeper family history, nationality, or origin story of every person with the name.
How many people named [First Name] Cassidy are there?
We can estimate any first + last name combination. Popular examples: Michael Cassidy, James Cassidy, John Cassidy. Search any combination on our homepage.
Where does this surname data come from?
Surname frequency data comes from the 2020 U.S. Census Bureau decennial surname tables. These list every surname appearing in the Census along with frequency rates and demographic breakdowns. Full methodology.
Search for a full name combination
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