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 son (b.~1927), then head of a 6-person household.
Age 13
b. ~1927
Male
Son
Born: Illinois
Single
1940 Census Record Details
| Census Year | 1940 |
| Location | Cook-County, Illinois |
| Surname | Kozlowski |
| Given Name | John |
| Relationship to Head | son |
| Sex | M |
| Color / Race | White |
| Age | 13 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago city |
| 1935 Residence (County) | Cook |
| Additional Details | |
| Highest Grade | 7 |
| 1935 Residence | Same place |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
| Township / Ward | Chicago City |
| Est. Birth Year | ~1927 |
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 |
|---|---|---|---|---|
| Josephine Kozlowski | Head | — | 42 | ~1898 |
| John Kozlowski | Son | — | 13 | ~1927 |
| Stella Kozlowski | Daughter | — | 16 | ~1924 |
| Joseph Kozlowski | Son | — | 21 | ~1919 |
| Frank Kozlowski | Son | — | 18 | ~1922 |
| Alice Kozlowski | Daughter | — | 10 | ~1930 |
Census Appearances
1930
Cook, Illinois
Son, age 3
Cook, Illinois · implied b. ~1927 — 7 household members
●
Primary link
· ~Confirmed · 2 sources
XGBoost
Household
| Surname | Kozlowski |
| Given Name | John |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 3 |
| Marital Status | Single |
| Birthplace | Illinois |
| Father's Birthplace | Illinois |
| Mother's Birthplace | Poland |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
1940
Cook-County, Illinois
Son, age 13
Cook-County, Illinois · implied b. ~1927 — 6 household members
| Surname | Kozlowski |
| Given Name | John |
| Relationship to Head | son |
| Sex | M |
| Color / Race | White |
| Age | 13 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago city |
| 1935 Residence (County) | Cook |
| Highest Grade | 7 |
| 1935 Residence | Same place |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
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.
Show:
This person
Anchor record
John Kozlowski
Son · 1940 · age 13 · b. ~1927 · Illinois
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Sibling
Joseph Kozlowski
Sibling · 1940 · age 21
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Alice Kozlowski
Sibling · 1940 · age 10
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Frank Kozlowski
Sibling · 1940 · age 18
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Stella Kozlowski
Sibling · 1940 · age 16
Source co-child of head (derived)
● Co-child · derived · ~0.88
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-t0627-00944-00858)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 1 | Wanda Fron | 18 | daughter | Hair Dresser | Illinois |
| 2 | Joseph Fron | 16 | son | New Worker | Illinois |
| 3 | Roman Fron | 14 | son | — | Illinois |
| 4 | Andrew Dziekanowski | 56 | Head | Laborer | Poland |
| 5 | Emelia Dziekanowski | 52 | Wife | — | Poland |
| 6 | Stanley Dziekanowski | 14 | son | — | Illinois |
| 7 | Stephen Czarnecki | 54 | Head | Laborer | Poland |
| 8 | Stephen Czarnecki | 16 | son | Laborer | Canada Eng |
| 9 | John Kowalewski | 23 | son | Laborer | Illinois |
| 10 | Jeanette Kowalewski | 22 | daughter | Laborer | Canada Eng |
| 11 | Josephine Kozlowski | 42 | Head | — | Illinois |
| 12 | Joseph Kozlowski | 21 | son | Dish Washer | Illinois |
| 13 | Frank Kozlowski | 18 | son | Dish Washer | Poland |
| 14 | Stella Kozlowski | 16 | daughter | — | Illinois |
| 15 | John Kozlowski THIS PERSON | 13 | son | — | Illinois |
| 16 | Alice Kozlowski | 10 | daughter | — | Illinois |
| 17 | Edward Berlinski | 31 | Head | Laborer | Illinois |
| 18 | Lillian Berlinski | 26 | Wife | Packing | Illinois |
| 19 | Helen Berlinski | 18 | sister | Laborer | Illinois |
| 20 | Regina Berlinski | 16 | sister | New Worker | Illinois |
| 21 | Joseph Berlinski | 12 | brother | — | Illinois |
| 22 | John Baczynski | 51 | Head | Laborer | Poland |
| 23 | Alice Baczynski | 32 | Wife | Laborer | New York |
| 24 | Andrew Baczynski | 18 | son | Upholsterer | West Virginia |
| 25 | Richard Baczynski | 14 | son | — | West Virginia |
| 26 | Cancel Baczynski | None | misinformed | — | — |
| 27 | John Stefaniak | 32 | Head | Laborer | Pennsylvania |
| 28 | Anna Stefaniak | 25 | Wife | — | Illinois |
| 29 | Stanley Stefaniak | 6 | son | — | Illinois |
| 30 | Alfreda Stefaniak | 4 | daughter | — | Illinois |
| 31 | Chester Stefaniak | 1 | son | — | Illinois |
| 32 | Frank Lukaszka | 30 | Head | Laborer | Illinois |
| 33 | Stephanie Lukaszka | 27 | Wife | — | Poland |
| 34 | Anna Lukaszka | 5 | daughter | — | Illinois |
| 35 | Edward Lukaszka | 3 | son | — | Illinois |
| 36 | Andrew Ciazynski | 45 | Head | Laborer | Poland |
| 37 | Antoinette Ciazynski | 15 | daughter | Housekeeper | Illinois |
| 38 | Sophia Ciazynski | 14 | daughter | — | Illinois |
| 39 | Frederick Jarecki | 25 | Head | Laborer | Illinois |
| 40 | Anna Jarecki | 25 | Wife | Laborer | New York |
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)