2000
#819
National surname rank
Recorded bearers 38,557
First available Census row
Per 100,000 14.29
Uncommon Last name
Mcmahon
Son of Mathghamhain, an Irish given name meaning "bear" or "cub."
According to the 2020 US Census Bureau surname tables, roughly 44,009 Americans carry the last name Mcmahon. That puts it at #893 in the national surname ranking, appearing at a frequency of 12.84 per 100,000 people (about 1 in 7,788 residents).
This page is the full Name Census profile for the Mcmahon 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 Mcmahon with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
44K
1 in 7,788
Census rank
#893
2020 decennial data
Per 100,000
12.8
Frequency rate
Recorded bearers
38K
uncommon in the US
Popularity narrative
The Census Bureau recorded 38,378 bearers of the surname Mcmahon in its 2020 decennial surname file. At a rate of 12.84 per 100,000 residents, it holds the 893rd position in the national surname ranking.
Among Census respondents with the surname Mcmahon, the largest self-reported group is White at 90.3%. The next largest groups are Hispanic (3.3%) and Two or More Races (3.0%).
Origin
Meaning and origin of Mcmahon
The surname McMahon originated in Ireland and derived from the Gaelic 'Mac Mathghamhna', meaning 'son of the bear'. It is an ancient Irish name that can be traced back to the 10th century. The McMahon clan was prominent in County Down, particularly in the baronies of Iveagh and Kinalea.
The McMahons were a powerful family who ruled over territories in County Down and parts of County Armagh. They were among the most important septs of the Oireacht Ui Eathach, a powerful dynasty that dominated much of Ulster from the 11th to the 16th century. The McMahons were noted for their involvement in various conflicts and battles during this period.
One of the earliest recorded references to the name is found in the Annals of Ulster, which mentions a chieftain named Mathghamhain (McMahon) who died in 1022. The name also appears in the Annals of the Four Masters, a chronicle of medieval Irish history compiled in the early 17th century.
In the 14th century, the McMahons were involved in a long-standing feud with the Savages, another prominent family in County Down. This conflict is mentioned in several historical records, including the Patent Rolls of James I, which refer to the "McMahons and Savages" as the two principal septs of the region.
Notable individuals with the surname McMahon include:
1. Heber McMahon (1600-1650), an Irish bishop and author who played a significant role in the Confederate Wars of the 1640s.
2. Maurice McMahon (1719-1792), an Irish-American merchant and politician who served as a delegate to the Continental Congress.
3. Martin McMahon (1835-1906), an Irish-American lawyer and politician who served as a US Senator from Ohio.
4. Sir Brian McMahon (1909-1998), an Irish judge and politician who served as the Attorney General of Ireland.
5. Ed McMahon (1923-2009), an American comedian and television personality best known as the longtime host of the Tonight Show Starring Johnny Carson.
The McMahon surname has been widespread throughout Ireland and has also been prominent in other countries with significant Irish diaspora populations, such as the United States, Canada, and Australia.
Demographics
Ancestry and ethnicity for Mcmahon
Among Census respondents with the surname Mcmahon, the largest self-reported group is White at 90.3%. The next largest groups are Hispanic (3.3%) and Two or More Races (3.0%).
The bar chart below shows how Mcmahon 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 Mcmahon surname at the time of the 2020 Census, not any inherent property of the name itself.
- White90.3% · 34,666
- Hispanic or Latino3.3% · 1,275
- Two or more races3.0% · 1,149
- Black or African American2.4% · 902
- Asian and Pacific Islander0.8% · 303
- American Indian and Alaska Native0.2% · 83
Timeline
Historical Census data for Mcmahon
Mcmahon 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
#883
National surname rank
Recorded bearers 39,411
+854 bearers (+2.2%)
Per 100,000 13.36
Rank movement Down 64 places
2020
#893
National surname rank
Recorded bearers 38,378
-1,033 bearers (-2.6%)
Per 100,000 12.84
Rank movement Down 10 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #819 | 38,557 | 14.29 | First available Census row | First available Census row |
| 2010 | #883 | 39,411 | 13.36 | +854 bearers (+2.2%) | Down 64 places |
| 2020 | #893 | 38,378 | 12.84 | -1,033 bearers (-2.6%) | Down 10 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 Mcmahon 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 | #883 | #893 | -1.1% |
| Count | 39,411 | 38,378 | -2.6% |
| Per 100K | 13.36 | 12.84 | -3.9% |
Between the 2010 and 2020 Census, the number of Mcmahon bearers went from 39,411 to 38,378 (-2.6% change). The surname moved down 10 positions in the national ranking, going from #883 to #893.
Notable bearers
Famous people with the surname Mcmahon
FAQ
Mcmahon surname: questions and answers
How many people in the U.S. have the surname Mcmahon?
Name Census estimates that about 44,009 living Americans carry the surname Mcmahon. Using the current population baseline, that works out to roughly 1 in 7,788 residents.
How common is Mcmahon?
Mcmahon ranks #893 in the 2020 Census surname tables and is classified on this site as "Uncommon." The Census recorded the name at a frequency of 12.84 per 100,000 residents, which is about 13 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 38,378 people with the surname Mcmahon. That is different from the site's living-bearer estimate (44,009), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 12.84 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 12.84 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 13 of them to have the surname Mcmahon.
Has Mcmahon become more or less common over time?
Between 2010 and 2020, the surname Mcmahon went from 39,411 recorded bearers to 38,378. That is a decrease of 1,033 (-2.6%). In the national ranking it fell from #883 to #893.
What does the Census say about the background of Mcmahon?
Among Census respondents with the surname Mcmahon, the largest self-reported group is White at 90.3%. The next largest groups are Hispanic (3.3%) and Two or More Races (3.0%). 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 Mcmahon in the 2020 Census, accounting for 90.3% (34,666 people in the source table).
What is the full ancestry breakdown?
Mcmahon appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (90.3%), Hispanic (3.3%), Two or More Races (3.0%). 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 Mcmahon (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 Mcmahon mean?
Son of Mathghamhain, an Irish given name meaning "bear" or "cub." 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 Mcmahon (12.84 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 last name Mcmahon?
If you just want to know how many Americans have the surname Mcmahon, HowManyOfMe.org gives you the headline number in one glance.