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.~1907), then head of a 5-person household.
Age 33
b. ~1907
Male
Head
Born: Illinois
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 | 33 |
| Marital Status | Married |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Additional Details | |
| Occupation | Lathe Hand |
| Industry | Forge & Pipe Works |
| Class of Worker | PW |
| Hours Worked | 40 |
| Income (1939) | 2300 |
| Highest Grade | No 8 |
| 1935 Residence | Same place |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
| Occupation | Lathe Hand |
| Township / Ward | Chicago |
| Est. Birth Year | ~1907 |
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.
5 people recorded at the same address in the 1940 census.
| Name | Relation to head | Relative to John | Age | Birth yr |
|---|---|---|---|---|
| Jean Kozlowski | Daughter | — | 8 | ~1932 |
| Marie Kozlowski | Spouse | — | 28 | ~1912 |
| Helen Kozlowski | Daughter | — | 11 | ~1929 |
| John Kozlowski | Head | — | 33 | ~1907 |
| Edward Kozlowski | Son | — | 3 | ~1937 |
Census Appearances
1930
Cook, Illinois
Son, age 23
Cook, Illinois · implied b. ~1907 — 6 household members
●
Primary link
· ~Confirmed · 2 sources
XGBoost
Household
| Surname | Kozlowski |
| Given Name | John |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 23 |
| Marital Status | Single |
| Birthplace | Illinois |
| Age at First Marriage | 23 |
| Father's Birthplace | Poland |
| Mother's Birthplace | Illinois |
| Occupation | Conductor |
| Industry | Street Car |
| Class of Worker | W |
| Can Read/Write | Yes |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
1940
Cook-County, Illinois
Head, age 33
Cook-County, Illinois · implied b. ~1907 — 5 household members
| Surname | Kozlowski |
| Given Name | John |
| Relationship to Head | head |
| Sex | M |
| Color / Race | White |
| Age | 33 |
| Marital Status | Married |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Occupation | Lathe Hand |
| Industry | Forge & Pipe Works |
| Class of Worker | PW |
| Hours Worked | 40 |
| Income (1939) | 2300 |
| Highest Grade | No 8 |
| 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.
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This person
Anchor record
John Kozlowski
Head · 1940 · age 33 · b. ~1907 · Illinois
★ You are viewing this record
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-t0627-00964-00125)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 1 | Mike Peankos | 48 | head | Nickle Buffer | Poland |
| 2 | Tillie Peankos | 48 | wife | — | Poland |
| 3 | Joe Peankos | 17 | son | — | Illinois |
| 4 | Lorretta Peankos | 14 | daughter | — | Illinois |
| 5 | Ted E Trochim | 37 | head | Bookkeeper | Illinois |
| 6 | Cecelia M Trochim | 24 | wife | Bookkeeper | Illinois |
| 7 | Valentine Jendrzejewski | 47 | head | Beauty Parlor Proprietor | Poland |
| 8 | Walter Jendrzejewski | 25 | son | Paint Mixer | Pennsylvania |
| 9 | Angeline Jendrzejewski | 20 | daughter | Paint Shader | Pennsylvania |
| 10 | Louis Stelmachowski | 60 | head | Tube Cutter | Poland |
| 11 | Cecelia Stelmachowski | 52 | wife | Furniture Finisher | Poland |
| 12 | Steve Stelmachowski | 30 | son | Truck Driver | Illinois |
| 13 | Sylvester Stelmachowski | 27 | son | Assembler In Radios | Illinois |
| 14 | Lucy Stelmachowski | 24 | daughter | Hospital Laundry | Illinois |
| 15 | Yolanda Stelmachowski | 21 | daughter | Coning In Hosiery Factory | Illinois |
| 16 | Leonard Stelmachowski | 20 | son | Sprayer | Illinois |
| 17 | Regina Stelmachowski | 13 | daughter | — | Illinois |
| 18 | Olympia Stelmachowski | 11 | daughter | — | Illinois |
| 19 | Ursula Stelmachowski | 64 | sister | — | Illinois |
| 20 | Joseph Mordzisz | 31 | head | Shoe Assembling | Illinois |
| 21 | Irene Mordzisz | 30 | wife | — | Illinois |
| 22 | Dorothy Mordzisz | 12 | daughter | — | Illinois |
| 23 | Irene Mordzisz | 10 | daughter | — | Illinois |
| 24 | Joseph Jr. Mordzisz | 7 | son | — | Illinois |
| 25 | Domoka Kuprewicz | 61 | head | — | Poland |
| 26 | Chester Kuprewicz | 29 | son | Radio Assembly | Illinois |
| 27 | Paul Warunek | 28 | head | Punch Press Operator | Poland |
| 28 | Lillian Warunek | 21 | wife | Wire Braiding Machine Operator | Illinois |
| 29 | Joseph Warunek | 52 | head | — | Poland |
| 30 | Valentine Warunek | 26 | son | Bread Divider | Illinois |
| 31 | George Warunek | 20 | son | Bakers Helper | Illinois |
| 32 | Veronica Warunek | 18 | daughter | New Worker | Illinois |
| 33 | Walter Fritz | 34 | son-in-law | Corrugator Operator | Pennsylvania |
| 34 | Stella Fritz | 27 | wife | — | Illinois |
| 35 | Anna Fritz | 5 | daughter | — | Illinois |
| 36 | John Kozlowski THIS PERSON | 33 | head | Lathe Hand | Illinois |
| 37 | Marie Kozlowski | 28 | wife | — | Illinois |
| 38 | Helen Kozlowski | 11 | daughter | — | Illinois |
| 39 | Jean Kozlowski | 8 | daughter | — | Illinois |
| 40 | Edward Kozlowski | 3 | son | — | 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)