JK
John Kozlowski — 1940 US Census Record
Linked across censuses1940 United States Federal Census · Cook-County, Illinois
Our Model Tree links this John Kozlowski across the 1930 and 1940 US Censuses in Cook-County, Illinois (XGBoost, ~Confirmed) — first a head (b.~1876), then head of a 6-person household.
Age 64
b. ~1876
Male
Head
Born: Poland
Married
1940 Census Record Details
| Census Year | 1940 |
| Location | Cook-County, Illinois |
| Surname | Kozlowski |
| Given Name | John |
| Relationship to Head | Head |
| Sex | M |
| Color / Race | White |
| Age | 64 |
| Marital Status | Married |
| Birthplace | Poland |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Naturalization Status | Naturalized |
| Additional Details | |
| Highest Grade | No 8 |
| 1935 Residence | Same house |
| Birth Country | Poland |
| Birthplace (normalized) | poland |
| Township / Ward | Chicago |
| Est. Birth Year | ~1876 |
Household Members
Census records only state relationship to the household head.
Pairwise kinship is derived (~90–95% accurate), not recorded.
Step/blended families and boarders can break it.
6 people recorded at the same address in the 1940 census.
| Name | Relation to head | Relative to John | Age | Birth yr |
|---|---|---|---|---|
| Walter Kozlowski | Son | — | 18 | ~1922 |
| John Kozlowski | Head | — | 64 | ~1876 |
| Bernice Kozlowski | Spouse | — | 56 | ~1884 |
| Harry Kozlowski | Son | — | 27 | ~1913 |
| Jack Kozlowski | Son | — | 26 | ~1914 |
| Bruno Kozlowski | Son | — | 20 | ~1920 |
Census Appearances
1930
Cook, Illinois
Head, age 53
Cook, Illinois · implied b. ~1877 — 6 household members
●
Primary link
· ~Confirmed · 2 sources
XGBoost
Household
| Surname | Kozlowski |
| Given Name | John |
| Relationship to Head | Head |
| Sex | M |
| Color / Race | White |
| Age | 53 |
| Marital Status | Married |
| Birthplace | Poland |
| Naturalization Status | Naturalized |
| Year of Immigration | 1904 |
| Age at First Marriage | 19 |
| Father's Birthplace | Poland |
| Mother's Birthplace | Poland |
| Can Read/Write | Yes |
| Mother Tongue | Polish |
| Home Owned/Rented | O |
| Home Value / Rent | 10000 |
| Radio Set | R |
| Veteran | No |
| Birth Country | Poland |
| Birthplace (normalized) | poland |
1940
Cook-County, Illinois
Head, age 64
Cook-County, Illinois · implied b. ~1876 — 6 household members
| Surname | Kozlowski |
| Given Name | John |
| Relationship to Head | Head |
| Sex | M |
| Color / Race | White |
| Age | 64 |
| Marital Status | Married |
| Birthplace | Poland |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Naturalization Status | Naturalized |
| Highest Grade | No 8 |
| 1935 Residence | Same house |
| Birth Country | Poland |
| Birthplace (normalized) | poland |
Model Tree
An inferred pedigree reconstructed from census links — up to 4 generations within the 1900–1950 window. Closer generations are built from household co-residence; deeper ones are bridged by following a relative to their own childhood census. Confidence compounds and weakens with each generation.
Our Model Tree links John Kozlowski across 2 US Census years (1930 and 1940) in 2 locations, using XGBoost record linkage.
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This person
Anchor record
John Kozlowski
Head · 1940 · age 64 · b. ~1876 · Illinois
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Confirmed / household (~0.90+)
Probable / derived (~0.65–0.89)
Candidate (<0.65, unverified)
Original Census Page
1940 US Federal Census — Cook-County, Illinois
Open full size
1940 US Federal Census — Cook-County, Illinois
Page Contents
40 people indexed on this census page (nara:1940:m-t0627-00944-00341)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 41 | Michael Rybak | 28 | Head | Laborer | Illinois |
| 42 | Marie Rybak | 26 | Wife | — | Illinois |
| 43 | Patrick Rybak | 2 | Son | — | Illinois |
| 44 | Frank Rybak | 53 | Head | Electrician | Germany |
| 45 | Elizabeth Rybak | 50 | Wife | — | Germany |
| 46 | Helen Rybak | 29 | Daughter | Inspector | Illinois |
| 47 | Gerard Rybak | 21 | Son | Laborer | Illinois |
| 48 | Anthony Rybak | 19 | Son | Laborer | Illinois |
| 49 | Joan Rybak | 12 | Daughter | — | Illinois |
| 50 | Frank Michalak | 37 | Head | Laborer | Illinois |
| 51 | Rose Michalak | 37 | Wife | — | Illinois |
| 52 | Frank Michalak | 1 | Son | — | Illinois |
| 53 | Valentine Wojtczak | 43 | Head | Laborer | Poland |
| 54 | Bernice Wojtczak | 44 | Wife | — | Poland |
| 55 | Henry Wojtczak | 24 | Son | Laborer | Illinois |
| 56 | Adeline Wojtczak | 22 | Daughter | Laborer | Illinois |
| 57 | Leonard Wojtczak | 13 | Son | — | Illinois |
| 58 | Richard Wojtczak | 10 | Son | — | Illinois |
| 59 | Victor Kajewski | 35 | Head | Truck Driver | Illinois |
| 60 | Betty Kajewski | 33 | Wife | — | Illinois |
| 61 | Joan Kajewski | 11 | Daughter | — | Illinois |
| 62 | Leonard Kajewski | 1 | Son | — | Illinois |
| 63 | John Kozlowski THIS PERSON | 64 | Head | — | Poland |
| 64 | Bernice Kozlowski | 56 | Wife | — | Poland |
| 65 | Harry Kozlowski | 27 | Son | Laborer | Illinois |
| 66 | Jack Kozlowski | 26 | Son | Salesman | Illinois |
| 67 | Bruno Kozlowski | 20 | Son | Laborer | Illinois |
| 68 | Walter Kozlowski | 18 | Son | New Worker | Illinois |
| 69 | Dominic Zypfrowski | 53 | Head | — | Poland |
| 70 | Raymond Zypfrowski | 32 | Son | Operator | Poland |
| 71 | Charlotte Zypfrowski | 22 | Daughter | Laborer | Illinois |
| 72 | Joseph Zypfrowski | 18 | Son | New Worker | Illinois |
| 73 | Estelle Kajewski | 57 | Head | — | Illinois |
| 74 | Louise Kajewski | 14 | Daughter | — | Illinois |
| 75 | Raymond Kajewski | 6 | Son | — | Illinois |
| 76 | Charles Goral | 24 | Head | Order Filler | Illinois |
| 77 | Celia Goral | 24 | Wife | — | Illinois |
| 78 | Paul Buryka | 29 | Head | Laborer | Illinois |
| 79 | Celia Buryka | 22 | Wife | Laborer | Wisconsin |
| 80 | Lucille Buryka | 5 | Daughter | — | Illinois |
About This Record & Model Tree
This record was independently indexed by YourRoots from the 1940 United States Federal Census (NARA). Our Model Tree links this person across census decades using XGBoost-based record linkage, with per-link confidence scores. Household corroboration strengthens the signal when co-residents appear on the same census pages in multiple years.
Source: National Archives and Records Administration (NARA)