2000
#11,032
National surname rank
Recorded bearers 2,644
First available Census row
Per 100,000 0.98
Rare Last name
Killough
An Irish toponymic surname derived from a place name meaning "church of the lough" or "church of the lake."
According to the 2020 US Census Bureau surname tables, roughly 2,676 Americans carry the last name Killough. That puts it at #12,630 in the national surname ranking, appearing at a frequency of 0.78 per 100,000 people (about 1 in 128,085 residents).
This page is the full Name Census profile for the Killough 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.
Bearers in the US
2.7K
1 in 128,085
Census rank
#12,630
2020 decennial data
Per 100,000
0.8
Frequency rate
Recorded bearers
2.3K
rare in the US
Popularity narrative
The Census Bureau recorded 2,334 bearers of the surname Killough in its 2020 decennial surname file. At a rate of 0.78 per 100,000 residents, it holds the 12630th position in the national surname ranking.
Among Census respondents with the surname Killough, the largest self-reported group is White at 89.3%. The next largest groups are Hispanic (3.9%) and Two or More Races (3.7%).
Origin
Meaning and origin of Killough
The surname Killough has its origins in Ireland, with the earliest records dating back to the 12th century. The name is derived from the Irish Gaelic words "cill" meaning church, and "achaidh" meaning field, suggesting that the name may have originated from a place name referring to a church or a settlement near a church in a field.
The name Killough is closely associated with County Down in Northern Ireland, where the town of Killough is located. This coastal town likely took its name from the same Gaelic roots, and it is believed that the surname originated in this area.
One of the earliest recorded instances of the surname Killough can be found in the Annals of Ulster, a chronicle of medieval Irish history, which mentions a person named Giolla Críost Ó Ceallaigh in the year 1184. This entry is considered one of the earliest written records of the name.
In the 16th century, the name Killough appeared in the Fiants of the Tudor Sovereigns, a collection of official records from the Tudor era. This suggests that the Killough family had established itself as a prominent name during this time period.
Notable individuals with the surname Killough throughout history include:
1. Sir John Killough (1575-1647), an Irish politician and landowner from County Down, who served as a member of the Irish Parliament in the early 17th century.
2. Thomas Killough (1753-1821), an Irish-born American farmer and soldier who fought in the American Revolutionary War.
3. William Killough (1802-1888), an American politician from Ohio who served as a U.S. Representative in the 35th Congress.
4. Mary Killough (1860-1939), an American educator and activist who advocated for women's rights and founded the Killough School for Girls in Virginia.
5. Robert Killough (1916-2001), a British-born American physicist who made significant contributions to the development of particle accelerators and nuclear physics research.
The surname Killough has also been associated with various place names, particularly in Ireland, such as Killough Bay and Killough Castle, both located in County Down. These place names further reinforce the connection between the surname and its geographical origins.
Demographics
Ancestry and ethnicity for Killough
Among Census respondents with the surname Killough, the largest self-reported group is White at 89.3%. The next largest groups are Hispanic (3.9%) and Two or More Races (3.7%).
The bar chart below shows how Killough 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 Killough surname at the time of the 2020 Census, not any inherent property of the name itself.
- White89.3% · 2,084
- Hispanic or Latino3.9% · 90
- Two or more races3.7% · 87
- Black or African American2.0% · 47
- Asian and Pacific Islander0.6% · 15
- American Indian and Alaska Native0.5% · 11
Timeline
Historical Census data for Killough
Killough 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
#11,810
National surname rank
Recorded bearers 2,650
+6 bearers (+0.2%)
Per 100,000 0.90
Rank movement Down 778 places
2020
#12,630
National surname rank
Recorded bearers 2,334
-316 bearers (-11.9%)
Per 100,000 0.78
Rank movement Down 820 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #11,032 | 2,644 | 0.98 | First available Census row | First available Census row |
| 2010 | #11,810 | 2,650 | 0.90 | +6 bearers (+0.2%) | Down 778 places |
| 2020 | #12,630 | 2,334 | 0.78 | -316 bearers (-11.9%) | Down 820 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 Killough 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 | #11,810 | #12,630 | -6.9% |
| Count | 2,650 | 2,334 | -11.9% |
| Per 100K | 0.90 | 0.78 | -13.2% |
Between the 2010 and 2020 Census, the number of Killough bearers went from 2,650 to 2,334 (-11.9% change). The surname moved down 820 positions in the national ranking, going from #11,810 to #12,630.
FAQ
Killough surname: questions and answers
How many people in the U.S. have the surname Killough?
Name Census estimates that about 2,676 living Americans carry the surname Killough. Using the current population baseline, that works out to roughly 1 in 128,085 residents.
How common is Killough?
Killough ranks #12,630 in the 2020 Census surname tables and is classified on this site as "Rare." The Census recorded the name at a frequency of 0.78 per 100,000 residents, which is about 1 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 2,334 people with the surname Killough. That is different from the site's living-bearer estimate (2,676), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 0.78 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 0.78 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 1 of them to have the surname Killough.
Has Killough become more or less common over time?
Between 2010 and 2020, the surname Killough went from 2,650 recorded bearers to 2,334. That is a decrease of 316 (-11.9%). In the national ranking it fell from #11,810 to #12,630.
What does the Census say about the background of Killough?
Among Census respondents with the surname Killough, the largest self-reported group is White at 89.3%. The next largest groups are Hispanic (3.9%) and Two or More Races (3.7%). 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 Killough in the 2020 Census, accounting for 89.3% (2,084 people in the source table).
What is the full ancestry breakdown?
Killough appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (89.3%), Hispanic (3.9%), Two or More Races (3.7%). 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 Killough (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 Killough mean?
An Irish toponymic surname derived from a place name meaning "church of the lough" or "church of the lake." 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 Killough (0.78 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 common is the surname Killough?
Want to know how common the surname Killough is? HowManyOfMe.org, our sister site, puts the living-bearer count front and centre.