JL
John Leahy — 1940 US Census Record
Linked across censuses1940 United States Federal Census · Middlesex-County, Massachusetts
Our Model Tree links this John Leahy across the 1930 and 1940 US Censuses in Middlesex-County, Massachusetts (XGBoost, ~Confirmed) — first a son (b.~1925), then head of a 6-person household.
Age 15
b. ~1925
Male
Son
Born: Massachusetts
Single
1940 Census Record Details
| Census Year | 1940 |
| Location | Middlesex-County, Massachusetts |
| Surname | Leahy |
| Given Name | John |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 15 |
| Marital Status | Single |
| Birthplace | Massachusetts |
| 1935 Residence (City) | Townsend |
| 1935 Residence (County) | Middlesex |
| Additional Details | |
| Class of Worker | 0 |
| Highest Grade | H 1 |
| 1935 Residence | Same place |
| Birth State | Massachusetts |
| Birth Country | United States |
| Birthplace (normalized) | massachusetts |
| Township / Ward | Townsend |
| Est. Birth Year | ~1925 |
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 John | Age | Birth yr |
|---|---|---|---|---|
| Robert Leahy | Son | — | 8 | ~1932 |
| John Leahy | Son | — | 15 | ~1925 |
| Louise Leahy | Daughter | — | 4 | ~1936 |
| Alice Leahy | Spouse | — | 34 | ~1906 |
| Frances Leahy | Daughter | — | 13 | ~1927 |
| Frank Leahy | Head | — | 38 | ~1902 |
Census Appearances
1930
Middlesex, Massachusetts
Son, age 5
Middlesex, Massachusetts · implied b. ~1925 — 2 household members
●
Primary link
· ~Confirmed · 2 sources
XGBoost
Household
| Surname | Leahy |
| Given Name | John |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 5 |
| Marital Status | Single |
| Birthplace | Massachusetts |
| Father's Birthplace | Massachusetts |
| Mother's Birthplace | Massachusetts |
| Occupation | none |
| Birth State | Massachusetts |
| Birth Country | United States |
| Birthplace (normalized) | massachusetts |
1940
Middlesex-County, Massachusetts
Son, age 15
Middlesex-County, Massachusetts · implied b. ~1925 — 6 household members
| Surname | Leahy |
| Given Name | John |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 15 |
| Marital Status | Single |
| Birthplace | Massachusetts |
| 1935 Residence (City) | Townsend |
| 1935 Residence (County) | Middlesex |
| Class of Worker | 0 |
| Highest Grade | H 1 |
| 1935 Residence | Same place |
| Birth State | Massachusetts |
| Birth Country | United States |
| Birthplace (normalized) | massachusetts |
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 15 · b. ~1925 · Massachusetts
★ You are viewing this record
Sibling
Robert Leahy
Sibling · 1940 · age 8
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Frances Leahy
Sibling · 1940 · age 13
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Louise Leahy
Sibling · 1940 · age 4
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 — Middlesex-County, Massachusetts
Open full size
1940 US Federal Census — Middlesex-County, Massachusetts
Page Contents
40 people indexed on this census page (nara:1940:m-t0627-01618-00223)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 1 | Vaino Mattila | 20 | Son | Laborer | Massachusetts |
| 2 | Vieno Mattila | 18 | Daughter | Housework | Massachusetts |
| 3 | Viola Mattila | 12 | Daughter | — | Massachusetts |
| 4 | Walter Mattila | 9 | Son | — | Massachusetts |
| 5 | John Mattila | 6 | Son | — | Massachusetts |
| 6 | Frank Leahy | 38 | Head | Truck Driver | Massachusetts |
| 7 | Alice Leahy | 34 | Wife | Stitcher | Massachusetts |
| 8 | John Leahy THIS PERSON | 15 | Son | — | Massachusetts |
| 9 | Frances Leahy | 13 | Daughter | — | Massachusetts |
| 10 | Robert Leahy | 8 | Son | — | Massachusetts |
| 11 | Louise Leahy | 4 | Daughter | — | Massachusetts |
| 12 | Frank Seasler | 81 | Head | — | Vermont |
| 13 | Loyal Searle | 57 | Head | Road Work | Vermont |
| 14 | Laura Searle | 57 | Wife | — | New Hampshire |
| 15 | Roy Searle | 18 | Son | — | Massachusetts |
| 16 | Lillian Stone | 53 | Head | — | New Hampshire |
| 17 | Kenneth Wheeler | 24 | Boarder | Stone Sawyer | Massachusetts |
| 18 | Alice Elizabeth | 19 | Niece | — | Massachusetts |
| 19 | William Elizabeth | 1 | Boarder | — | Massachusetts |
| 20 | James Gibney | 58 | Head | — | Massachusetts |
| 21 | Jennie Devine | 54 | Sister | — | New Jersey |
| 22 | Mary F. Smith | 52 | Sister | Postmistress | Massachusetts |
| 23 | James Smith | 42 | Brother-in-law | — | Canada |
| 24 | Louis Steinberg | 41 | Head | Manager | Russia |
| 25 | Clara Steinberg | 38 | Wife | — | Massachusetts |
| 26 | Eva Steinberg | 11 | Daughter | — | New Hampshire |
| 27 | Clinton Mackey | 64 | Head | Farm | New York |
| 28 | Elizabeth Mackey | 68 | Wife | — | New York |
| 29 | George Jones | 73 | Head | — | Massachusetts |
| 30 | H. Ella Jones | 74 | Wife | — | New Hampshire |
| 31 | William Ball | 69 | Head | — | Rhode Island |
| 32 | Josephine Ball | 57 | Wife | — | Rhode Island |
| 33 | Stephen Ball | 39 | Son | Road Work | Rhode Island |
| 34 | Florence Ball | 8 | Daughter | — | Massachusetts |
| 35 | James Lambert | 47 | Head | Foreman | Massachusetts |
| 36 | Florence Lambert | 40 | Wife | — | Massachusetts |
| 37 | Frank H. Hoxie | 64 | Head | Farmer | New York |
| 38 | Belle B. Hoxie | 52 | Owner | — | New Hampshire |
| 39 | James S. Hoxie | 16 | Owner | — | New Hampshire |
| 40 | Nikolai Hallio | 55 | Head | Farmer | Finland |
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)