MK
Mary Kowalski — 1940 US Census Record
Linked across censuses1940 United States Federal Census · Cook-County, Illinois
Our Model Tree links this Mary Kowalski across the 1930 and 1940 US Censuses in Cook-County, Illinois (XGBoost, ~Confirmed) — first a daughter (b.~1920), then head of a 8-person household.
Age 20
b. ~1920
Female
Daughter
Born: Illinois
Single
1940 Census Record Details
| Census Year | 1940 |
| Location | Cook-County, Illinois |
| Surname | Kowalski |
| Given Name | Mary |
| Relationship to Head | daughter |
| Sex | F |
| Color / Race | White |
| Age | 20 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago City |
| 1935 Residence (County) | Cook |
| Additional Details | |
| Occupation | machine operator |
| Industry | Publishing Co |
| Class of Worker | PW |
| Income (1939) | 26 |
| Highest Grade | No 8 |
| 1935 Residence | Same house |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
| Occupation | Machine Operator |
| Township / Ward | Chicago City |
| Est. Birth Year | ~1920 |
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.
8 people recorded at the same address in the 1940 census.
| Name | Relation to head | Relative to Mary | Age | Birth yr |
|---|---|---|---|---|
| Mary Kowalski | Daughter | — | 20 | ~1920 |
| Stanley Kowalski | Son | — | 21 | ~1919 |
| Frank Kowalski | Head | — | 55 | ~1885 |
| Virginia Kowalski | Daughter | — | 16 | ~1924 |
| Joseph Kowalski | Son | — | 24 | ~1916 |
| John Kowalski | Son | — | 13 | ~1927 |
| Emily Kowalski | Daughter | — | 25 | ~1915 |
| Francis Kowalski | Spouse | — | 54 | ~1886 |
Census Appearances
1930
Cook, Illinois
Daughter, age 9
Cook, Illinois · implied b. ~1921 — 3 household members
●
Primary link
· ~Confirmed · 2 sources
XGBoost
Household
| Surname | Kowalski |
| Given Name | Margaret |
| Relationship to Head | Daughter |
| Sex | F |
| Color / Race | White |
| Age | 9 |
| Marital Status | Single |
| Birthplace | Illinois |
| Father's Birthplace | Russia |
| Mother's Birthplace | Michigan |
| Can Read/Write | Yes |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
1940
Cook-County, Illinois
Daughter, age 20
Cook-County, Illinois · implied b. ~1920 — 8 household members
| Surname | Kowalski |
| Given Name | Mary |
| Relationship to Head | daughter |
| Sex | F |
| Color / Race | White |
| Age | 20 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago City |
| 1935 Residence (County) | Cook |
| Occupation | machine operator |
| Industry | Publishing Co |
| Class of Worker | PW |
| Income (1939) | 26 |
| Highest Grade | No 8 |
| 1935 Residence | Same house |
| 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 Kowalski across 2 US Census years (1930 and 1940) in 2 locations, using XGBoost record linkage.
Show:
This person
Anchor record
Mary Kowalski
Daughter · 1940 · age 20 · b. ~1920 · Illinois
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Sibling
Joseph Kowalski
Sibling · 1940 · age 24
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Emily Kowalski
Sibling · 1940 · age 25
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Virginia Kowalski
Sibling · 1940 · age 16
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Stanley Kowalski
Sibling · 1940 · age 21
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
John Kowalski
Sibling · 1940 · age 13
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-t0627-00936-00650)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 1 | Dorothy Kowalaski | 17 | daughter | None | Illinois |
| 2 | Sylvia Kowalaski | 17 | daughter | None | Illinois |
| 3 | Frank Kowalski | 36 | Head | Beautician | Illinois |
| 4 | Mary Kowalski | 26 | wife | Butcher | Illinois |
| 5 | Diana Marie Kowalski | 7 | daughter | — | Illinois |
| 6 | Joseph Kozubowski | 61 | Head | Chipper | Poland |
| 7 | Joseph Janich | 45 | partner | — | Poland |
| 8 | Sophie Zachocki | 65 | Head | — | Poland |
| 9 | Alec Zachocki | 36 | son | Laborer | Illinois |
| 10 | Dorothy Zachocki | 15 | daughter | — | Illinois |
| 11 | Edward Zachocki | 13 | son | — | Illinois |
| 12 | Raymond Zachocki | 12 | son | — | Illinois |
| 13 | Frank Kowalski | 55 | Head | Laborer | Poland |
| 14 | Francis Kowalski | 54 | wife | — | Poland |
| 15 | Emily Kowalski | 25 | daughter | Housework | Illinois |
| 16 | Joseph Kowalski | 24 | son | Laborer | Illinois |
| 17 | Stanley Kowalski | 21 | son | Laborer | Illinois |
| 18 | Mary Kowalski THIS PERSON | 20 | daughter | Machine Operator | Illinois |
| 19 | Virginia Kowalski | 16 | daughter | — | Illinois |
| 20 | John Kowalski | 13 | son | — | Illinois |
| 21 | Rudolph Szewczyk | 24 | Head | Scrap Hoist Operator | Texas |
| 22 | Chester Szewczyk | 23 | wife | Curtain Maker | Illinois |
| 23 | John Glowacki | 40 | Head | Gas Operator | Poland |
| 24 | Wanda Glowacki | 30 | wife | — | Illinois |
| 25 | Kasimir Glowacki | 67 | Head | — | Poland |
| 26 | Michalena Glowacki | 67 | wife | — | Poland |
| 27 | Stella Glowacki | 30 | daughter | Folder | Illinois |
| 28 | Micky Glowacki | 28 | son | Chipper | Illinois |
| 29 | Walter Glowacki | 26 | son | Chipper | Illinois |
| 30 | Cecilia Glowacki | 25 | daughter | — | Illinois |
| 31 | Mitchell Mihaljevich | 23 | Head | Tube Cutter | Minnesota |
| 32 | Sophie Mihaljevich | 23 | wife | Label Pieces | Illinois |
| 33 | Stephen Adams | 33 | Head | Rougher | Illinois |
| 34 | Anastasia Adams | 33 | wife | Packer | Illinois |
| 35 | Andrew Adams | 7 | son | — | Illinois |
| 36 | Alvin Szajkowski | 30 | Head | Crane Operator | Wisconsin |
| 37 | Lottie Szajkowski | 33 | wife | — | Illinois |
| 38 | Robert Szajkowski | 0 | son | — | Illinois |
| 39 | Michal Siutka | 49 | Head | Conductor | Poland |
| 40 | Mary Siutka | 44 | wife | — | Poland |
Related Census Records
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)