2000
#10,327
National surname rank
Recorded bearers 2,859
First available Census row
Per 100,000 1.06
Rare Last name
Mcilwain
A Scottish toponymic surname referring to someone from a place called Macilwham, likely derived from a Gaelic personal name.
According to the 2020 US Census Bureau surname tables, roughly 3,257 Americans carry the last name Mcilwain. That puts it at #10,736 in the national surname ranking, appearing at a frequency of 0.95 per 100,000 people (about 1 in 105,236 residents).
This page is the full Name Census profile for the Mcilwain 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 Mcilwain with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
3.3K
1 in 105,236
Census rank
#10,736
2020 decennial data
Per 100,000
1.0
Frequency rate
Recorded bearers
2.8K
rare in the US
Popularity narrative
The Census Bureau recorded 2,840 bearers of the surname Mcilwain in its 2020 decennial surname file. At a rate of 0.95 per 100,000 residents, it holds the 10736th position in the national surname ranking.
Among Census respondents with the surname Mcilwain, the largest self-reported group is White at 61.9%. The next largest groups are Black (31.4%) and Two or More Races (3.3%).
Origin
Meaning and origin of Mcilwain
The surname McIlwain has its origins in Scotland, where it first emerged in the 13th century. It is a habitational name derived from the Gaelic "mac Ghille Fhuathain," which means "son of the servant of St. Fillan." This suggests that the earliest bearers of the name were employed in the service of a church dedicated to St. Fillan, a popular Scottish saint.
The name is closely associated with the region of Perthshire, where the village of Killin was a significant center for the veneration of St. Fillan. It is likely that the McIlwains were originally from this area or had some connection to the local church or monastery.
One of the earliest recorded instances of the name appears in the Exchequer Rolls of Scotland in 1329, where a John McYlwyne is mentioned. Other early spellings include McIlwyne, McYlwham, and McIlquham, reflecting the variations in pronunciation and spelling that were common in medieval times.
In the 16th century, the McIlwains were established as landowners in Perthshire, with several members of the family holding estates in the area around Killin. One notable figure was John McIlwain, who was appointed as the Chamberlain of Strathearn in 1548.
As the name spread throughout Scotland and beyond, it produced several individuals of note. Sir William McIlwain (1685-1761) was a Scottish merchant and landowner who served as Lord Provost of Edinburgh from 1749 to 1751. Thomas McIlwain (1824-1903) was a prominent industrialist and founder of the McIlwain Foundry in Belfast, Northern Ireland.
In the literary world, Charles Howard McIlwain (1871-1968) was an American historian and scholar of constitutional law, best known for his work on the Magna Carta. He served as the president of the American Historical Association in 1936.
The McIlwain name also has a long-standing connection to the United States, with many bearers of the name arriving as early settlers in the 17th and 18th centuries. One of the earliest recorded instances is that of John McIlwain, who was granted land in Virginia in 1670.
Throughout its history, the surname McIlwain has been carried by individuals from various walks of life, including clergymen, academics, politicians, and businessmen. While its origins can be traced back to a specific region of Scotland and a connection to the veneration of St. Fillan, the name has since spread across the globe, with bearers contributing to the rich tapestry of human endeavor.
Demographics
Ancestry and ethnicity for Mcilwain
Among Census respondents with the surname Mcilwain, the largest self-reported group is White at 61.9%. The next largest groups are Black (31.4%) and Two or More Races (3.3%).
The bar chart below shows how Mcilwain 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 Mcilwain surname at the time of the 2020 Census, not any inherent property of the name itself.
- White61.9% · 1,759
- Black or African American31.4% · 891
- Two or more races3.3% · 94
- Hispanic or Latino2.7% · 77
- Asian and Pacific Islander0.4% · 11
- American Indian and Alaska Native0.3% · 8
Timeline
Historical Census data for Mcilwain
Mcilwain 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
#10,657
National surname rank
Recorded bearers 3,002
+143 bearers (+5.0%)
Per 100,000 1.02
Rank movement Down 330 places
2020
#10,736
National surname rank
Recorded bearers 2,840
-162 bearers (-5.4%)
Per 100,000 0.95
Rank movement Down 79 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #10,327 | 2,859 | 1.06 | First available Census row | First available Census row |
| 2010 | #10,657 | 3,002 | 1.02 | +143 bearers (+5.0%) | Down 330 places |
| 2020 | #10,736 | 2,840 | 0.95 | -162 bearers (-5.4%) | Down 79 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 Mcilwain 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 | #10,657 | #10,736 | -0.7% |
| Count | 3,002 | 2,840 | -5.4% |
| Per 100K | 1.02 | 0.95 | -6.8% |
Between the 2010 and 2020 Census, the number of Mcilwain bearers went from 3,002 to 2,840 (-5.4% change). The surname moved down 79 positions in the national ranking, going from #10,657 to #10,736.
FAQ
Mcilwain surname: questions and answers
How many people in the U.S. have the surname Mcilwain?
Name Census estimates that about 3,257 living Americans carry the surname Mcilwain. Using the current population baseline, that works out to roughly 1 in 105,236 residents.
How common is Mcilwain?
Mcilwain ranks #10,736 in the 2020 Census surname tables and is classified on this site as "Rare." The Census recorded the name at a frequency of 0.95 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 2,840 people with the surname Mcilwain. That is different from the site's living-bearer estimate (3,257), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 0.95 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 0.95 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 Mcilwain.
Has Mcilwain become more or less common over time?
Between 2010 and 2020, the surname Mcilwain went from 3,002 recorded bearers to 2,840. That is a decrease of 162 (-5.4%). In the national ranking it fell from #10,657 to #10,736.
What does the Census say about the background of Mcilwain?
Among Census respondents with the surname Mcilwain, the largest self-reported group is White at 61.9%. The next largest groups are Black (31.4%) and Two or More Races (3.3%). 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 Mcilwain in the 2020 Census, accounting for 61.9% (1,759 people in the source table).
What is the full ancestry breakdown?
Mcilwain appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (61.9%), Black (31.4%), Two or More Races (3.3%). 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 Mcilwain (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 Mcilwain mean?
A Scottish toponymic surname referring to someone from a place called Macilwham, likely derived from a Gaelic personal name. 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 Mcilwain (0.95 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 Mcilwain?
HowManyOfMe.org, our sister site, answers that with the living-bearer count in one glance.