MK
Mary Kozlowski — 1940 US Census Record
Linked across censuses1940 United States Federal Census · Cook-County, Illinois
Our Model Tree links this Mary Kozlowski across the 1930 and 1940 US Censuses in Cook-County, Illinois (XGBoost, ~Confirmed) — first a daughter (b.~1927), then head of a 6-person household.
Age 13
b. ~1927
Female
Daughter
Born: Illinois
Single
1940 Census Record Details
| Census Year | 1940 |
| Location | Cook-County, Illinois |
| Surname | Kozlowski |
| Given Name | Mary |
| Relationship to Head | Daughter |
| Sex | F |
| Color / Race | White |
| Age | 13 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Additional Details | |
| Income (1939) | 0 |
| Highest Grade | Hs 2 |
| 1935 Residence | Same place |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
| Township / Ward | Chicago |
| 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 Mary | Age | Birth yr |
|---|---|---|---|---|
| Philis Kozlowski | Daughter | — | 25 | ~1915 |
| Stanley Kozlowski | Head | — | 53 | ~1887 |
| Joseph Kozlowski | Son | — | 13 | ~1927 |
| Martha Kozlowski | Spouse | — | 51 | ~1889 |
| Mary Kozlowski | Daughter | — | 13 | ~1927 |
| Eleanore Kozlowski | Daughter | — | 11 | ~1929 |
Census Appearances
1930
Cook, Illinois
Daughter, age 3
Cook, Illinois · implied b. ~1927 — 3 household members
●
Primary link
· ~Confirmed · 2 sources
XGBoost
Household
| Surname | Kozlowski |
| Given Name | Mary |
| Relationship to Head | daughter |
| Sex | F |
| 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
Daughter, age 13
Cook-County, Illinois · implied b. ~1927 — 6 household members
| Surname | Kozlowski |
| Given Name | Mary |
| Relationship to Head | Daughter |
| Sex | F |
| Color / Race | White |
| Age | 13 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Income (1939) | 0 |
| Highest Grade | Hs 2 |
| 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 Mary Kozlowski across 2 US Census years (1930 and 1940) in 2 locations, using XGBoost record linkage.
Show:
This person
Anchor record
Mary Kozlowski
Daughter · 1940 · age 13 · b. ~1927 · Illinois
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Sibling
Joseph Kozlowski
Sibling · 1940 · age 13
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Philis Kozlowski
Sibling · 1940 · age 25
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Eleanore Kozlowski
Sibling · 1940 · age 11
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-t0627-00943-00703)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 1 | Minnie Steinkamp | 53 | Wife | — | Illinois |
| 2 | Edna Steinkamp | 26 | Daughter | File Clerk | Illinois |
| 3 | Misinformed Only 3 Instead Of 5 | None | — | — | — |
| 4 | Edward Zippel | 60 | Head | — | Poland |
| 5 | Ethel Zippel | 25 | Daughter | Saleslady | Illinois |
| 6 | Arthur Zippel | 23 | Son | New Worker | Illinois |
| 7 | Evelyn Zippel | 18 | Daughter | Card Filler | Illinois |
| 8 | William Zorek | 47 | Head | Alloy Curater | Illinois |
| 9 | Stella Zorek | 41 | Wife | — | Illinois |
| 10 | Leonard Zorek | 35 | Son | — | Illinois |
| 11 | John Ligocki | 16 | Son | — | Illinois |
| 12 | Anna Harrigan | 48 | Head | — | Poland |
| 13 | Bernice Harrigan | 15 | Daughter | — | Illinois |
| 14 | Elmer Sherach | 33 | Head | Street Construe | Illinois |
| 15 | Lottie Sherach | 31 | Wife | — | Illinois |
| 16 | Stanley Kozlowski | 53 | Head | Loading Truck | Poland |
| 17 | Martha Kozlowski | 51 | Wife | — | Poland |
| 18 | Philis Kozlowski | 25 | Daughter | Bag Maker | Poland |
| 19 | Mary Kozlowski THIS PERSON | 13 | Daughter | — | Illinois |
| 20 | Joseph Kozlowski | 13 | Son | — | Illinois |
| 21 | Eleanore Kozlowski | 11 | Daughter | — | Illinois |
| 22 | Chester Dayan | 35 | Head | Mural Painter | Illinois |
| 23 | Ann Dayan | 31 | Wife | — | Illinois |
| 24 | Ann Dayan | 8 | Daughter | — | Illinois |
| 25 | Chester Dayan | 7 | Son | — | Illinois |
| 26 | Priscilla Dayan | 4 | Daughter | — | Illinois |
| 27 | Joseph Zelewski | 52 | Head | Electrician Helper | Poland |
| 28 | Lulla Zelewski | 46 | Wife | — | Poland |
| 29 | Casimira Zelewski | 19 | Daughter | Sewing Machine Oper | Illinois |
| 30 | Edward Zelewski | 14 | Son | — | Illinois |
| 31 | Walter Wojciechowski | 25 | Head | Golf Club Shipper | Illinois |
| 32 | Stephanie Wojciechowski | 24 | Wife | — | Illinois |
| 33 | Joyce Wojciechowski | 1 | Daughter | — | Illinois |
| 34 | Lula Czarny | 47 | Head | — | Illinois |
| 35 | Jean Czarny | 23 | Daughter | Laundry Sorter | Illinois |
| 36 | Martha Czarny | 23 | Daughter | Laundry Sorter | Illinois |
| 37 | Joseph Czarny | 19 | Son | Stock Boy | Illinois |
| 38 | Joan Czarny | 3 | Daughter | — | Illinois |
| 39 | Rose Frankowski | 32 | Head | — | Illinois |
| 40 | Mary Ellen Frankowski | 5 | Daughter | — | 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)