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.~1928), then head of a 14-person household.
Age 12
b. ~1928
Male
Son
Born: Illinois
Single
1940 Census Record Details
| Census Year | 1940 |
| Location | Cook-County, Illinois |
| Surname | Kozlowski |
| Given Name | John Jr. |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 12 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Additional Details | |
| Highest Grade | 6 |
| 1935 Residence | Illinois |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
| Township / Ward | Chicago |
| Est. Birth Year | ~1928 |
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.
14 people recorded at the same address in the 1940 census.
| Name | Relation to head | Relative to John | Age | Birth yr |
|---|---|---|---|---|
| Joan Kozlowski | Daughter | — | 2 | ~1938 |
| Stanley Kozlowski | Other | — | 38 | ~1902 |
| Josephine Kozlowski | Other | — | 70 | ~1870 |
| John Kozlowski | Head | — | 45 | ~1895 |
| Robert Kozlowski | Son | — | 4 | ~1936 |
| Mary Kozlowski | Spouse | — | 42 | ~1898 |
| Edward Kozlowski | Son | — | 18 | ~1922 |
| Dolores Kozlowski | Daughter | — | 8 | ~1932 |
| John Kozlowski | Son | — | 12 | ~1928 |
| Richard Kozlowski | Son | — | 6 | ~1934 |
| Helen Kozlowski | Daughter | — | 16 | ~1924 |
| Thomas Kozlowski | Son | — | 1 | ~1939 |
| Theresa Kozlowski | Daughter | — | 10 | ~1930 |
| Alice Kozlowski | Daughter | — | 14 | ~1926 |
Census Appearances
1930
Cook, Illinois
Son, age 3
Cook, Illinois · implied b. ~1927 — 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 | 3 |
| Marital Status | Single |
| Birthplace | Illinois |
| Father's Birthplace | Illinois |
| Mother's Birthplace | Illinois |
| Occupation | none |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
1940
Cook-County, Illinois
Son, age 12
Cook-County, Illinois · implied b. ~1928 — 14 household members
| Surname | Kozlowski |
| Given Name | John Jr. |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 12 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Highest Grade | 6 |
| 1935 Residence | Illinois |
| 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 12 · b. ~1928 · Illinois
★ You are viewing this record
Sibling
Helen Kozlowski
Sibling · 1940 · age 16
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Joan Kozlowski
Sibling · 1940 · age 2
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Robert Kozlowski
Sibling · 1940 · age 4
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Theresa Kozlowski
Sibling · 1940 · age 10
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Alice Kozlowski
Sibling · 1940 · age 14
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Dolores Kozlowski
Sibling · 1940 · age 8
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Richard Kozlowski
Sibling · 1940 · age 6
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Edward Kozlowski
Sibling · 1940 · age 18
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Thomas Kozlowski
Sibling · 1940 · age 1
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-t0627-00946-00825)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 41 | John Kozlowski | 45 | Head | Laborer | Poland |
| 42 | Mary Kozlowski | 42 | Wife | — | Poland |
| 43 | Edward Kozlowski | 18 | Son | Clerk | Illinois |
| 44 | Helen Kozlowski | 16 | Daughter | — | Illinois |
| 45 | Alice Kozlowski | 14 | Daughter | — | Illinois |
| 46 | John Jr. Kozlowski THIS PERSON | 12 | Son | — | Illinois |
| 47 | Theresa Kozlowski | 10 | Daughter | — | Illinois |
| 48 | Dolores Kozlowski | 8 | Daughter | — | Illinois |
| 49 | Richard Kozlowski | 6 | Son | — | Illinois |
| 50 | Robert Kozlowski | 4 | Son | — | Illinois |
| 51 | Joan Kozlowski | 2 | Daughter | — | Illinois |
| 52 | Thomas Kozlowski | 1 | Son | — | Illinois |
| 53 | Josephine Kozlowski | 70 | Mother | — | Poland |
| 54 | Stanley Kozlowski | 38 | Brother | Laborer | Poland |
| 55 | Frank Szymanski | 52 | Head | Machinist | Poland |
| 56 | Stella Szymanski | 48 | Wife | — | Poland |
| 57 | Frank Jr. Szymanski | 24 | Son | Clerk | Illinois |
| 58 | Eleanor Szymanski | 22 | Daughter | Stenographer | Illinois |
| 59 | Raymond Szymanski | 20 | Son | Laborer | Illinois |
| 60 | Gertrude Szymanski | 18 | Daughter | — | Illinois |
| 61 | Arthur Szymanski | 16 | Son | — | Illinois |
| 62 | Dorothy Szymanski | 14 | Daughter | — | Illinois |
| 63 | Eugene Szymanski | 12 | Son | — | Illinois |
| 64 | Lorraine Szymanski | 10 | Daughter | — | Illinois |
| 65 | Robert Szymanski | 8 | Son | — | Illinois |
| 66 | Richard Szymanski | 6 | Son | — | Illinois |
| 67 | Donald Szymanski | 4 | Son | — | Illinois |
| 68 | Geraldine Szymanski | 2 | Daughter | — | Illinois |
| 69 | Joseph Nowak | 40 | Head | Carpenter | Poland |
| 70 | Mary Nowak | 38 | Wife | — | Poland |
| 71 | Joseph Jr. Nowak | 16 | Son | — | Illinois |
| 72 | Edward Nowak | 14 | Son | — | Illinois |
| 73 | Florence Nowak | 12 | Daughter | — | Illinois |
| 74 | Alice Nowak | 10 | Daughter | — | Illinois |
| 75 | Theresa Nowak | 8 | Daughter | — | Illinois |
| 76 | Rita Nowak | 6 | Daughter | — | Illinois |
| 77 | Dolores Nowak | 4 | Daughter | — | Illinois |
| 78 | Robert Nowak | 2 | Son | — | Illinois |
| 79 | Joan Nowak | 1 | Daughter | — | Illinois |
| 80 | Thomas Nowak | 0 | 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)