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.~1923), then head of a 6-person household.
Age 17
b. ~1923
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 | 17 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago City |
| 1935 Residence (County) | Cook |
| Additional Details | |
| Class of Worker | 0 |
| Hours Worked | 0 |
| Highest Grade | Hs 3 |
| 1935 Residence | Same place |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
| Township / Ward | Chicago City |
| Est. Birth Year | ~1923 |
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 |
|---|---|---|---|---|
| William Kozlowski | Son | — | 22 | ~1918 |
| Joseph Kozlowski | Son | — | 29 | ~1911 |
| Anne Kozlowski | Spouse | — | 48 | ~1892 |
| Jacob Kozlowski | Head | — | 57 | ~1883 |
| John Kozlowski | Son | — | 17 | ~1923 |
| Henry Kozlowski | Son | — | 15 | ~1925 |
Census Appearances
1930
Cook, Illinois
Son, age 6
Cook, Illinois · implied b. ~1924 — 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 | 6 |
| Marital Status | Single |
| Birthplace | Illinois |
| Father's Birthplace | New York |
| Mother's Birthplace | Illinois |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
1940
Cook-County, Illinois
Son, age 17
Cook-County, Illinois · implied b. ~1923 — 6 household members
| Surname | Kozlowski |
| Given Name | John |
| Relationship to Head | son |
| Sex | M |
| Color / Race | White |
| Age | 17 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago City |
| 1935 Residence (County) | Cook |
| Class of Worker | 0 |
| Hours Worked | 0 |
| Highest Grade | Hs 3 |
| 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 17 · b. ~1923 · Illinois
★ You are viewing this record
Sibling
Joseph Kozlowski
Sibling · 1940 · age 29
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
William Kozlowski
Sibling · 1940 · age 22
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Henry Kozlowski
Sibling · 1940 · age 15
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-t0627-00940-00805)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 41 | Irene Dolega | 3 | daughter | — | Illinois |
| 42 | Caroline Dolega | 1 | daughter | — | Illinois |
| 43 | Victoria Cisek | 65 | Head | — | Poland |
| 44 | Leo Cisek | 29 | son | Laborer | Illinois |
| 45 | Jacob Kozlowski | 57 | Head | Laborer | Poland |
| 46 | Anne Kozlowski | 48 | wife | — | Poland |
| 47 | Joseph Kozlowski | 29 | son | Laborer | Illinois |
| 48 | William Kozlowski | 22 | son | New Worker | Illinois |
| 49 | John Kozlowski THIS PERSON | 17 | son | — | Illinois |
| 50 | Henry Kozlowski | 15 | son | — | Illinois |
| 51 | Edward Savicz | 29 | Head | Truck Driver | Illinois |
| 52 | Jane Savicz | 28 | wife | — | Illinois |
| 53 | Edward Jr. Savicz | 4 | son | — | Illinois |
| 54 | Steven Savicz | 24 | head | Sales Clerk | Illinois |
| 55 | Lottie Savicz | 21 | wife | — | Illinois |
| 56 | Frances Savicz | 50 | mother | — | Lithuania |
| 57 | — | None | — | — | — |
| 58 | Francis Radavich | 51 | Head | Laborer | Lithuania |
| 59 | Valeria Radavich | 46 | wife | — | Lithuania |
| 60 | Ewald Radavich | 22 | son | Laborer | Illinois |
| 61 | Jean Radavich | 20 | daughter | Housework | Illinois |
| 62 | Dorothy Radavich | 18 | daughter | New Worker | Illinois |
| 63 | Valeria Radavich | 14 | daughter | — | Illinois |
| 64 | Charles Ankusas | 57 | Head | Power Shovel Opr. | Lithuania |
| 65 | Placida Ankusas | 55 | wife | — | Lithuania |
| 66 | Josephine Pollick | 28 | step-daughter | Packer | Iowa |
| 67 | Leonard Pluta | 46 | Head | Molder | Poland |
| 68 | Frances Pluta | 43 | wife | — | Poland |
| 69 | Chester Pluta | 22 | son | Press Operator | Illinois |
| 70 | Virginia Pluta | 13 | daughter | — | Illinois |
| 71 | Benedict Pluta | 12 | son | — | Illinois |
| 72 | Theresa Pluta | 7 | daughter | — | Illinois |
| 73 | Edward O'Connor | 23 | son-in-law | Carcleaner | Illinois |
| 74 | Agnes O'Connor | 18 | daughter | — | Illinois |
| 75 | Sandra M. O'Connor | 0 | grand-daughter | — | Illinois |
| 76 | Joseph T. Doyle | 41 | Head | Switchman | Illinois |
| 77 | Anna Doyle | 34 | wife | — | Illinois |
| 78 | Joseph A. Doyle | 9 | son | — | Illinois |
| 79 | Edward Emmich | 36 | roomer | Bartender | Maryland |
| 80 | John Adamecz | 34 | Head | Laborer | 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)