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 10-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 city |
| 1935 Residence (County) | Cook |
| Additional Details | |
| Occupation | Conductor |
| Industry | Street Railway |
| Class of Worker | PW |
| Hours Worked | 48 |
| Income (1939) | 1600 |
| Highest Grade | Hs 1 |
| 1935 Residence | Same Place |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
| Occupation | Conductor |
| Township / Ward | Chicago City |
| 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.
10 people recorded at the same address in the 1940 census.
| Name | Relation to head | Relative to John | Age | Birth yr |
|---|---|---|---|---|
| Elmer Ociepka | Son | — | 17 | ~1923 |
| John Kozlowski | Head | — | 33 | ~1907 |
| Carol Kozlowski | Daughter | — | 2 | ~1938 |
| Lottie Ociepka | Daughter | — | 21 | ~1919 |
| Judy Kozlowski | Daughter | — | 9 | ~1931 |
| Caroline Ociepka | Other | — | 59 | ~1881 |
| Nora Ociepka | Daughter | — | 29 | ~1911 |
| John Ociepka | Son | — | 23 | ~1917 |
| Mary Ociepka | Daughter | — | 25 | ~1915 |
| Sophie Kozlowski | Spouse | — | 35 | ~1905 |
Census Appearances
1930
Cook, Illinois
Son, age 22
Cook, Illinois · implied b. ~1908 — 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 | 22 |
| Marital Status | Single |
| Birthplace | Illinois |
| Father's Birthplace | Poland |
| Mother's Birthplace | Poland |
| 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 — 10 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 city |
| 1935 Residence (County) | Cook |
| Occupation | Conductor |
| Industry | Street Railway |
| Class of Worker | PW |
| Hours Worked | 48 |
| Income (1939) | 1600 |
| Highest Grade | Hs 1 |
| 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
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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-t0627-00974-00659)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 1 | Helena Pawlowska | 19 | Head | Retail Sales Clerk | Poland |
| 2 | Sabina Pawlowska | 16 | Daughter | — | Poland |
| 3 | Peter Kobylecki | 51 | Head | Baker | Poland |
| 4 | Kornelia Kobylecki | 35 | Wife | — | Poland |
| 5 | John Burzynski | 34 | Head | Salesman - Milk | Illinois |
| 6 | Eleanor Burzynski | 32 | Wife | — | Illinois |
| 7 | Helene Burzynski | 8 | Daughter | — | Illinois |
| 8 | Fred Salzmann | 46 | Head | Machinist | Russia |
| 9 | Marie Salzmann | 48 | Wife | — | Russia |
| 10 | Eleonore Salzmann | 17 | Daughter | Stenographer | Illinois |
| 11 | Roland Salzmann | 17 | Son | Errand Boy | Illinois |
| 12 | Clifford Salzmann | 11 | Son | — | Illinois |
| 13 | Bernard Helvin | 42 | Head | Tracer | Germany |
| 14 | Margaret Helvin | 34 | Wife | — | Germany |
| 15 | George Helvin | 45 | Son | — | Illinois |
| 16 | Bernard Jr. Helvin | 6 | Son | — | Illinois |
| 17 | Michael Bakawa | 25 | Head | Inspector | Illinois |
| 18 | Olga Bakawa | 23 | Wife | Enameler | Illinois |
| 19 | Robert Bakawa | 1 | Son | — | Illinois |
| 20 | Anna Milgarcha | 66 | Mother-in-law | — | Poland |
| 21 | Martin Koziarz | 54 | Head | Machin. Ailer | Poland |
| 22 | Margaret Koziarz | 47 | Wife | Cleaning | Illinois |
| 23 | Edward Koziarz | 23 | Son | Machin. Assistant | Illinois |
| 24 | Edwin Koziarz | 20 | Son | Tool Maker | Illinois |
| 25 | Margaret Kolodziej | 83 | Mother-in-law | — | Poland |
| 26 | John Guzman | 29 | Head | Shipping Clerk | Pennsylvania |
| 27 | Annette Guzman | 24 | Wife | — | Illinois |
| 28 | Ronald Guzman | 0 | Son | — | Illinois |
| 29 | Joseph Slegaszynski | 59 | Brother-in-law | Leather Press | Poland |
| 30 | Sophie Slegaszynski | 55 | Sister-in-law | — | Poland |
| 31 | John Kozlowski THIS PERSON | 33 | Head | Conductor | Illinois |
| 32 | Sophie Kozlowski | 35 | Wife | — | Illinois |
| 33 | Judy Kozlowski | 9 | Daughter | — | Illinois |
| 34 | Carol Kozlowski | 2 | Daughter | — | Illinois |
| 35 | Caroline Ociepka | 59 | Mother | — | Poland |
| 36 | Nora Ociepka | 29 | Daughter | — | Illinois |
| 37 | Mary Ociepka | 25 | Daughter | — | Illinois |
| 38 | John Ociepka | 23 | Son | Tool Maker | Illinois |
| 39 | Lottie Ociepka | 21 | Daughter | Sales Lady | Illinois |
| 40 | Elmer Ociepka | 17 | 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)