MK
Mary Koch — 1940 US Census Record
Linked across censuses1940 United States Federal Census · Cook-County, Illinois
Our Model Tree links this Mary Koch across the 1930 and 1940 US Censuses in Cook-County, Illinois (XGBoost, ~Confirmed) — first a daughter (b.~1926), then head of a 6-person household.
Age 14
b. ~1926
Female
Daughter
Born: Illinois
Single
1940 Census Record Details
| Census Year | 1940 |
| Location | Cook-County, Illinois |
| Surname | Koch |
| Given Name | Mary Ann |
| Relationship to Head | Daughter |
| Sex | F |
| Color / Race | White |
| Age | 14 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago City |
| 1935 Residence (County) | Cook |
| Additional Details | |
| Class of Worker | 0 |
| Highest Grade | 7 |
| 1935 Residence | Same place |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
| Township / Ward | Chicago City |
| Est. Birth Year | ~1926 |
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 |
|---|---|---|---|---|
| Joseph Koch | Son | — | 9 | ~1931 |
| John Koch | Son | — | 9 | ~1931 |
| Carola Koch | Spouse | — | 40 | ~1900 |
| Mary Koch | Daughter | — | 14 | ~1926 |
| Carol Koch | Daughter | — | 8 | ~1932 |
| Carl Koch | Head | — | 40 | ~1900 |
Census Appearances
1930
Cook, Illinois
Daughter, age 3
Cook, Illinois · implied b. ~1927 — 6 household members
●
Primary link
· ~Confirmed · 2 sources
XGBoost
Household
| Surname | Koch |
| Given Name | Mary Ann |
| Relationship to Head | Daughter |
| Sex | F |
| Color / Race | White |
| Age | 3 |
| Marital Status | Single |
| Birthplace | Illinois |
| Father's Birthplace | Germany |
| Mother's Birthplace | Germany |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
1940
Cook-County, Illinois
Daughter, age 14
Cook-County, Illinois · implied b. ~1926 — 6 household members
| Surname | Koch |
| Given Name | Mary Ann |
| Relationship to Head | Daughter |
| Sex | F |
| Color / Race | White |
| Age | 14 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago City |
| 1935 Residence (County) | Cook |
| Class of Worker | 0 |
| Highest Grade | 7 |
| 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 Koch across 2 US Census years (1930 and 1940) in 2 locations, using XGBoost record linkage.
Show:
This person
Anchor record
Mary Koch
Daughter · 1940 · age 14 · b. ~1926 · Illinois
★ You are viewing this record
Sibling
Carol Koch
Sibling · 1940 · age 8
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Joseph Koch
Sibling · 1940 · age 9
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
John Koch
Sibling · 1940 · age 9
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-t0627-00940-00030)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 1 | Lester Mueller | 43 | Head | Clerk | Wisconsin |
| 2 | Julia Mueller | 40 | Wife | — | Indiana |
| 3 | Lester Mueller | 12 | Son | — | Illinois |
| 4 | William Mueller | 8 | Son | — | Illinois |
| 5 | Ernest Solomon | 44 | Head | Machinist | Germany |
| 6 | Jessie Solomon | 43 | Wife | — | Hungary |
| 7 | Stephen Ellison | 58 | Head | — | Czecho Slovakia |
| 8 | Mary Ellison | 57 | Wife | — | Czecho Slovakia |
| 9 | Margaret Ellison | 26 | Daughter | Clerk | Illinois |
| 10 | Frank Ellison | 24 | Son | Manager | Illinois |
| 11 | John Kolonvige | 36 | Head | Salesman | Illinois |
| 12 | Marie Kolonvige | 26 | Wife | — | Illinois |
| 13 | Joseph Kolonvige | 10 | Son | — | Illinois |
| 14 | John Kolonvige | 1 | Son | — | Illinois |
| 15 | Delbert Watson | 52 | Head | Millwright | Canada English |
| 16 | Rose Watson | 41 | Wife | — | Illinois |
| 17 | Eleanor Watson | 22 | Daughter | Coil Winder | Illinois |
| 18 | William Watson | 20 | Son | New Worker | Illinois |
| 19 | Frances Watson | 13 | Daughter | — | Illinois |
| 20 | Knute Agren | 69 | Head | — | Sweden |
| 21 | Alida Agren | 68 | Wife | — | Sweden |
| 22 | Carl Koch | 40 | Head | Barber | Germany |
| 23 | Carola Koch | 40 | Wife | — | Germany |
| 24 | Mary Ann Koch THIS PERSON | 14 | Daughter | — | Illinois |
| 25 | Joseph Koch | 9 | Son | — | Illinois |
| 26 | John Koch | 9 | Son | — | Illinois |
| 27 | Carol Jean Koch | 8 | Daughter | — | Illinois |
| 28 | Arenk Janis | 50 | Head | Printer | Illinois |
| 29 | Zyla Janis | 50 | Wife | — | Illinois |
| 30 | Raoul Janis | 26 | Son | Welder | Illinois |
| 31 | Melvin Janis | 25 | Son | Attendant | Illinois |
| 32 | Wilbur Janis | 21 | Son | Trucker | Illinois |
| 33 | Peter Janis | 17 | Son | — | Illinois |
| 34 | Carl Janis | 12 | Son | — | Illinois |
| 35 | Carl Anderson | 78 | Head | Shoe Repairing | Sweden |
| 36 | Aline Anderson | 75 | Wife | — | Sweden |
| 37 | Henry Nodenberg | 43 | Head | Tinner | Sweden |
| 38 | Sigrid Nodenberg | 41 | Wife | — | Norway |
| 39 | Ellen Nodenberg | 10 | Daughter | — | Illinois |
| 40 | Marion Nodenberg | 8 | 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)