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.~1917), then head of a 7-person household.
Age 23
b. ~1917
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 | 23 |
| Marital Status | Single |
| Birthplace | Massachusetts |
| 1935 Residence (City) | Cambridge |
| 1935 Residence (County) | Middlesex |
| Additional Details | |
| Occupation | New Worker |
| Class of Worker | GW |
| Hours Worked | 3 |
| Income (1939) | 5 |
| Highest Grade | H 4 |
| 1935 Residence | Same Place |
| Birth State | Massachusetts |
| Birth Country | United States |
| Birthplace (normalized) | massachusetts |
| Occupation | New Worker |
| Township / Ward | Cambridge |
| Est. Birth Year | ~1917 |
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.
7 people recorded at the same address in the 1940 census.
| Name | Relation to head | Relative to John | Age | Birth yr |
|---|---|---|---|---|
| John Leahy | Head | — | 57 | ~1883 |
| Mary Leahy | Spouse | — | 57 | ~1883 |
| Katherine Leahy | Daughter | — | 29 | ~1911 |
| Francis Leahy | Son | — | 21 | ~1919 |
| Thomas Leahy | Son | — | 25 | ~1915 |
| John Leahy | Son | — | 23 | ~1917 |
| Louise Leahy | Daughter | — | 17 | ~1923 |
Census Appearances
1930
Worcester, Massachusetts
Son, age 12
Worcester, Massachusetts · implied b. ~1918 — 5 household members
●
Primary link
· ~Confirmed · 2 sources
XGBoost
Household
| Surname | Leahy |
| Given Name | John |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 12 |
| Marital Status | Single |
| Birthplace | Massachusetts |
| Father's Birthplace | Massachusetts |
| Mother's Birthplace | Massachusetts |
| Occupation | none |
| Can Read/Write | Yes |
| Birth State | Massachusetts |
| Birth Country | United States |
| Birthplace (normalized) | massachusetts |
1940
Middlesex-County, Massachusetts
Son, age 23
Middlesex-County, Massachusetts · implied b. ~1917 — 7 household members
| Surname | Leahy |
| Given Name | John |
| Relationship to Head | Son |
| Sex | M |
| Color / Race | White |
| Age | 23 |
| Marital Status | Single |
| Birthplace | Massachusetts |
| 1935 Residence (City) | Cambridge |
| 1935 Residence (County) | Middlesex |
| Occupation | New Worker |
| Class of Worker | GW |
| Hours Worked | 3 |
| Income (1939) | 5 |
| Highest Grade | H 4 |
| 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 23 · b. ~1917 · Massachusetts
★ You are viewing this record
Sibling
Louise Leahy
Sibling · 1940 · age 17
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Thomas Leahy
Sibling · 1940 · age 25
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Katherine Leahy
Sibling · 1940 · age 29
Source co-child of head (derived)
● Co-child · derived · ~0.88
Sibling
Francis Leahy
Sibling · 1940 · age 21
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-t0627-01685-00202)
| Line | Name | Age | Relation | Occupation | Birthplace |
|---|---|---|---|---|---|
| 1 | Elaine Donnell | 16 | Wife | — | Massachusetts |
| 2 | James Moran | 76 | Head | Moulder | Massachusetts |
| 3 | Nellie Moran | 67 | Wife | — | Eire |
| 4 | Mary Moran | 40 | Daughter | Stenographer | Massachusetts |
| 5 | Helen Moran | 38 | Daughter | Stenographer | Massachusetts |
| 6 | John Moran | 33 | Son | Salesman | Massachusetts |
| 7 | Leonard Mckenney | 54 | Head | Painter | Canada English |
| 8 | Laura Mckenney | 50 | Wife | — | Massachusetts |
| 9 | Hester Barrett | 45 | Lodger | Auditor | Maine |
| 10 | Eugene Henry | 26 | Lodger | Supervisor | Canada French |
| 11 | — | 72 | Lodger | — | Maine |
| 12 | John Leahy | 57 | Head | Electrician | Massachusetts |
| 13 | Mary Leahy | 57 | Wife | — | Massachusetts |
| 14 | Katherine Leahy | 29 | Daughter | Comptometer Op | Massachusetts |
| 15 | Thomas Leahy | 25 | Son | Errand Man | Massachusetts |
| 16 | John Leahy THIS PERSON | 23 | Son | New Worker | Massachusetts |
| 17 | Francis Leahy | 21 | Son | Stitcher | Massachusetts |
| 18 | Louise Leahy | 17 | Daughter | — | Massachusetts |
| 19 | Eleanor Campbell | 63 | Head | — | Canada English |
| 20 | Lilly Campbell | 35 | Daughter | Office Manager | Massachusetts |
| 21 | Ella Jenkins | 71 | Lodger | — | Canada English |
| 22 | Walter Trefer | 40 | Lodger | New Worker | Massachusetts |
| 23 | Blanche Meagher | 32 | Lodger | Nurse Reg | Massachusetts |
| 24 | John Fitzpatrick | 47 | Lodger | Ins. Salesman | Northern Ireland |
| 25 | Helen Fitzpatrick | 49 | Wife | — | Massachusetts |
| 26 | Doris Shend | 35 | Lodger | Reg Nurse | Massachusetts |
| 27 | Clifford Mckenney | 26 | Head | Gas Pumper | Massachusetts |
| 28 | Virginia Mckenney | 22 | Wife | Typist | Ohio |
| 29 | Elizabeth Humphreys | 52 | Head | — | Eire |
| 30 | Lillian Humphreys | 19 | Daughter | Secretary | Massachusetts |
| 31 | Roger Hurd | 24 | Lodger | Machinist | Maine |
| 32 | John Davis | 30 | Lodger | Machinist | Maine |
| 33 | Mary Crocker | 38 | Head | Reg. Nurse | Penna |
| 34 | Alice Clarke | 38 | Head | — | Massachusetts |
| 35 | Betty Clarke | 2 | Daughter | — | Massachusetts |
| 36 | Vivian Porter | 36 | Head | Stitcher | New York |
| 37 | Sexton June Porter | 17 | Daughter | Stitcher | Massachusetts |
| 38 | Anne Davis | 30 | Head | Waitress | Maine |
| 39 | Helen Davis | 23 | Sister | Waitress | Maine |
| 40 | Nicholas Koundouros | 44 | Head | Cook | Greece |
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)