How many John Kozlowski census records do you have?

We have 3387 US Census records for John Kozlowski, from 1900 to 1950, across 35 states and DC.

What's in a John Kozlowski census record?

You'll see John's age, birthplace, occupation, and relationship to the head of household — plus everyone else who lived in the same home. For 1940 and 1950 records, you can also view the original handwritten census page.

How do I use census records for family research?

Census records are a snapshot of a family every 10 years. You can follow John Kozlowski's household over time — see when children appear, when people move states, and who's living together. YourRoots connects census data with Tree Matching and AI tools so you can build out your tree faster.

Are John Kozlowski census records free?

Yes. All John Kozlowski census records on YourRoots are free to search and view — no subscription required. We built our own index from the original federal census images.

Which census years and states cover John Kozlowski?

We have John Kozlowski records from the 1900 through 1950 US Federal Census, across 35 states and DC. Use the year and state filters to narrow your results.

How do I find John Kozlowski in the census?

Start by narrowing the year and state. If you know an approximate birth year, use the age column to match — census age minus the census year gives you a birth year estimate. Household members, birthplace, and occupation help confirm you have the right person.

What is the Model Tree for John Kozlowski?

The Model Tree is YourRoots' unique feature that links a person across multiple census decades and reconstructs their likely family — parents, siblings, spouse, and children — based on household patterns. It turns isolated records into a connected family network.

Where does the census data come from?

All records originate from the US Federal Census microfilm digitized by NARA (National Archives and Records Administration). YourRoots re-indexed the original page images using modern AI, catching names and details that older transcriptions missed.

John Kozlowski — US Census Records & Model Tree

We found 3387 free census records for John Kozlowski across 6 census years (1900–1950), in 35 states and DC and 166 counties. Each record includes our Model Tree — the same person linked across decades using machine learning, with per-link confidence scores.

John Kozlowski Census Records by State & County

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Showing of 3387 records for John Kozlowski US Census, ranked by Model Tree richness

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Year	Name	Age	Location	Birthplace	Occupation	Relation
1930	John Kozlowski		None, New York	Poland	—	Head
1930	John Kozlowski		Bergen, New Jersey	New Jersey	—	Son
1940	John Jr. Kozlowski	12	Cook-County, Illinois	Illinois	—	Son
1930	John Kozlowski		Hudson, New Jersey	New Jersey	Carpenter	Son
1910	John Kozlowski		Erie, New York	Germany	Laborer	Head
1940	John Kozlowski	24	Middlesex-County, New Jersey	New Jersey	Laborer	Son
1930	John J Kozlowski		Allegheny, Pennsylvania	Pennsylvania	—	Son
1930	John Kozlowski		Allegheny, Pennsylvania	Poland	Roller	Head
1940	John Kozlowski	33	Cook-County, Illinois	Illinois	Conductor	Head
1940	John Kozlowski	16	Essex-County, New Jersey	New Jersey	—	Son
1920	John Kozlowski		Erie, New York	Austria	Machinist	Son
1940	John Kozlowski	51	Laporte-County, Indiana	Poland	Moulder	Head
1920	John Kozlowski		Mercer, New Jersey	Lithuania	Laborer	Head
1940	John Kozlowski	18	Schenectady-County, New York	Poland	—	Son
1940	John Kozlowski	17	Cook-County, Illinois	Illinois	—	Son
1920	John Kozlowski		Erie, New York	Russia Polish	Carman	Head
1940	John Kozlowski	21	Hudson-County, New Jersey	New Jersey	Truck Driver	Son
1930	John Kozlowski		Middlesex, New Jersey	New Jersey	—	Son
1940	John Kozlowski	53	Cook-County, Illinois	Poland	Foreman	Head
1940	John Kozlowski	64	Cook-County, Illinois	Poland	—	Head
1940	John Kozlowski	13	Cook-County, Illinois	Illinois	—	Son
1940	John Kozlowski	59	Milwaukee-County, Wisconsin	Poland	Laborer	Head
1940	John Kozlowski	25	Wayne-County, Michigan	Illinois	Truck Driver	Son
1920	John Kozlowski		Erie, New York	Poland	Laborer	Head
1940	John Kozlowski	22	Erie-County, New York	New York	New Worker	Son
1930	John Kozlowski		Cook, Illinois	Illinois	—	Son
1940	John Kozlowski	14	Cuyahoga-County, Ohio	Ohio	—	Son
1930	John Kozlowski		Essex, Massachusetts	Poland	Baker	Head
1940	John Kozlowski	33	Cook-County, Illinois	Illinois	Lathe Hand	Head
1940	John Kozlowski	31	Wayne-County, Michigan	Missouri	Plater	Head

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About John Kozlowski US Census Records & Model Tree

We've indexed 3387 free, proprietary US Census records for John Kozlowski across 1900–1950, covering 35 states and DC: Alabama, Arkansas, California, Colorado, Connecticut, Delaware, District of Columbia, Florida, Hawaii, Illinois, Indiana, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Dakota, Texas, Utah, Virginia, Washington, West Virginia, Wisconsin.

Each record includes our Model Tree — a longitudinal reconstruction that links the same person across census decades using machine learning (XGBoost record linkage). Every link carries a confidence score: Verified (≥0.99), Confirmed (≥0.95), or Linked (lower confidence). This tells you not just what the census says, but how reliably we've connected records across time.

Every record also shows the full household — who John lived with, their ages, birthplaces, and occupations. For 1940 and 1950 records, you can view the original handwritten census page from the National Archives.

How we build the Model Tree. YourRoots independently indexes US Census records from NARA microfilm and links persons across decades using XGBoost-based record linkage. Each link's confidence is a per-pair match score from the model. Household corroboration (co-residents appearing on the same census pages in multiple years) strengthens the signal. The Model Tree is not a family tree submitted by users — it's reconstructed from the census data itself.

Last updated: July 30, 2026

Frequently Asked Questions

: We have 3387 US Census records for John Kozlowski, from 1900 to 1950, across 35 states and DC.
: You'll see John's age, birthplace, occupation, and relationship to the head of household — plus everyone else who lived in the same home. For 1940 and 1950 records, you can also view the original handwritten census page.
: Census records are a snapshot of a family every 10 years. You can follow John Kozlowski's household over time — see when children appear, when people move states, and who's living together. YourRoots connects census data with Tree Matching and AI tools so you can build out your tree faster.
: Yes. All John Kozlowski census records on YourRoots are free to search and view — no subscription required. We built our own index from the original federal census images.
: We have John Kozlowski records from the 1900 through 1950 US Federal Census, across 35 states and DC. Use the year and state filters above to narrow your results.
: Start by narrowing the year and state. If you know an approximate birth year, use the age column to match — census age minus the census year gives you a birth year estimate. Household members, birthplace, and occupation help confirm you have the right person.
: The Model Tree is YourRoots' unique feature that links a person across multiple census decades and reconstructs their likely family — parents, siblings, spouse, and children — based on household patterns. It turns isolated records into a connected family network.
: All records originate from the US Federal Census microfilm digitized by NARA (National Archives and Records Administration). YourRoots re-indexed the original page images using modern AI, catching names and details that older transcriptions missed.

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