JL
John Leahy — 1940 US Census Record
Linked across censuses1940 United States Federal Census · Cook-County, Illinois
Our Model Tree links this John Leahy across the 1930 and 1940 US Censuses in Cook-County, Illinois (XGBoost, ~Confirmed) — first a son (b.~1919), then head of a 5-person household.
Age 21
b. ~1919
Male
Son
Born: Illinois
Single
1940 Census Record Details
| Census Year | 1940 |
| Location | Cook-County, Illinois |
| Surname | Leahy |
| Given Name | John Jr |
| Relationship to Head | son |
| Sex | M |
| Color / Race | White |
| Age | 21 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Additional Details | |
| Occupation | New Worker |
| Highest Grade | H-4 |
| 1935 Residence | Same place |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
| Occupation | New Worker |
| Township / Ward | Chicago |
| Est. Birth Year | ~1919 |
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.
5 people recorded at the same address in the 1940 census.
| Name | Relation to head | Relative to John | Age | Birth yr |
|---|---|---|---|---|
| Catherine Leahy | Daughter | — | 17 | ~1923 |
| William Leahy | Son | — | 19 | ~1921 |
| John Leahy | Son | — | 21 | ~1919 |
| John Leahy | Head | — | 52 | ~1888 |
| Julia Leahy | Spouse | — | 47 | ~1893 |
Census Appearances
1930
Cook, Illinois
Son, age 11
Cook, Illinois · implied b. ~1919 — 5 household members
●
Primary link
· ~Confirmed · 2 sources
XGBoost
Household
| Surname | Leahy |
| Given Name | John Jr |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 11 |
| Marital Status | Single |
| Birthplace | Illinois |
| Father's Birthplace | Ireland-Free |
| Mother's Birthplace | Ireland-Free |
| Can Read/Write | Yes |
| Birth State | Illinois |
| Birth Country | United States |
| Birthplace (normalized) | illinois |
1940
Cook-County, Illinois
Son, age 21
Cook-County, Illinois · implied b. ~1919 — 5 household members
| Surname | Leahy |
| Given Name | John Jr |
| Relationship to Head | son |
| Sex | M |
| Color / Race | White |
| Age | 21 |
| Marital Status | Single |
| Birthplace | Illinois |
| 1935 Residence (City) | Chicago |
| 1935 Residence (County) | Cook |
| Occupation | New Worker |
| Highest Grade | H-4 |
| 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 Leahy across 2 US Census years (1930 and 1940) in 2 locations, using XGBoost record linkage.
Show:
This person
Anchor record
John Leahy
Son · 1940 · age 21 · b. ~1919 · Illinois
★ You are viewing this record
Sibling
Catherine Leahy
Sibling · 1940 · age 17
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
William Leahy
Sibling · 1940 · age 19
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-t0627-00979-00072)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 41 | Barbara A King | 2 | daughter | — | Illinois |
| 42 | Peter A King | 1 | son | — | Illinois |
| 43 | Edward P King | 0 | son | — | Illinois |
| 44 | Luke P. Walsh | 57 | Head | Salesman | England |
| 45 | Loretta Walsh | 47 | wife | None | Illinois |
| 46 | Luke P. Jr. Walsh | 23 | son | Clerk | Illinois |
| 47 | George Walsh | 22 | son | Sheet-Metal Worker | Illinois |
| 48 | Dorothy Walsh | 17 | daughter | None | Illinois |
| 49 | Ethel Meltzer | 45 | Head | Salesman | Illinois |
| 50 | Catherine Meltzer | 45 | wife | None | Illinois |
| 51 | Lorraine Meltzer | 20 | daughter | Saleslady | Illinois |
| 52 | Marvin Meltzer | 15 | son | None | Illinois |
| 53 | Margaret Walsh | 67 | Head | None | Illinois |
| 54 | James F Walsh | 34 | son | Accountant | Illinois |
| 55 | Joseph Kadolph | 32 | Head | Auto Mechanic | Iowa |
| 56 | Geraldine Kadolph | 30 | wife | None | Kansas |
| 57 | Doris J. Kadolph | 9 | daughter | None | Iowa |
| 58 | Carroll Kadolph | 5 | son | None | Iowa |
| 59 | Marvin Kadolph | 3 | son | None | Iowa |
| 60 | John Leahy | 52 | Head | Ticket Agent | Eire |
| 61 | Julia Leahy | 47 | wife | None | Eire |
| 62 | John Jr Leahy THIS PERSON | 21 | son | New Worker | Illinois |
| 63 | William Leahy | 19 | son | Assembler | Illinois |
| 64 | Catherine Leahy | 17 | daughter | None | Illinois |
| 65 | Theresa Kenny | 60 | Head | Attendant | Illinois |
| 66 | Margaret Kane | 30 | daughter | Clerk Commercial Dept | Illinois |
| 67 | Margaret Collins | 65 | Head | None | Ohio |
| 68 | Theresa Culhane | 39 | daughter | None | Illinois |
| 69 | Donald Culhane | 4 | grandson | None | Illinois |
| 70 | John J. Currie | 60 | brother | Porter | Illinois |
| 71 | Patrick Connelly | 71 | Head | Owner + Manager | Eire |
| 72 | Margaret Connelly | 71 | wife | None | Eire |
| 73 | Patrick M. Connelly | 34 | son | Electrical Engineer | Eire |
| 74 | James Talamo | 66 | Head | Owner + Manager | Italy |
| 75 | Catherine Talamo | 56 | wife | None | Italy |
| 76 | Bruno Talamo | 20 | son | Apprentice Butcher | Italy |
| 77 | Constance Talamo | 18 | daughter | None | Italy |
| 78 | Joseph Talamo | 30 | son | Butcher | Italy |
| 79 | Rose Talamo | 26 | daughter-in-law | None | Italy |
| 80 | Joseph Trada | 37 | Head | Bar Tender | 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)