How many Mary Hennessy census records do you have?

We have 2731 US Census records for Mary Hennessy, from 1900 to 1950, across 46 states and DC.

What's in a Mary Hennessy census record?

You'll see Mary's age, birthplace, occupation, and relationship to the head of household — plus everyone else who lived in the same home. For 1940 and 1950 records, you can also view the original handwritten census page.

How do I use census records for family research?

Census records are a snapshot of a family every 10 years. You can follow Mary Hennessy's household over time — see when children appear, when people move states, and who's living together. YourRoots connects census data with Tree Matching and AI tools so you can build out your tree faster.

Are Mary Hennessy census records free?

Yes. All Mary Hennessy census records on YourRoots are free to search and view — no subscription required. We built our own index from the original federal census images.

Which census years and states cover Mary Hennessy?

We have Mary Hennessy records from the 1900 through 1950 US Federal Census, across 46 states and DC. Use the year and state filters to narrow your results.

How do I find Mary Hennessy in the census?

Start by narrowing the year and state. If you know an approximate birth year, use the age column to match — census age minus the census year gives you a birth year estimate. Household members, birthplace, and occupation help confirm you have the right person.

What is the Model Tree for Mary Hennessy?

The Model Tree is YourRoots' unique feature that links a person across multiple census decades and reconstructs their likely family — parents, siblings, spouse, and children — based on household patterns. It turns isolated records into a connected family network.

Where does the census data come from?

All records originate from the US Federal Census microfilm digitized by NARA (National Archives and Records Administration). YourRoots re-indexed the original page images using modern AI, catching names and details that older transcriptions missed.

Mary Hennessy — US Census Records & Model Tree

We found 2731 free census records for Mary Hennessy across 6 census years (1900–1950), in 46 states and DC and 366 counties. Each record includes our Model Tree — the same person linked across decades using machine learning, with per-link confidence scores.

Mary Hennessy Census Records by State & County

Records per state:

Census Record Search

First Name

Middle Name

Last Name (Required)

Census Year

State

Birth Year

Year Range

Birthplace

Age From

Age To

Exact match: Name Location Year

Alternate First Names (comma-separated)

Alternate Last Names (comma-separated)

County

Sex

Marital Status

Race

Relationship to Head

Occupation

Census Page ID

Family Members (in same household)

Search Records

Showing of 2731 records for Mary Hennessy US Census, ranked by Model Tree richness

No records match your filters.

Year	Name	Age	Location	Birthplace	Occupation	Relation
1940	Mary Jo Hennessy	22	Ramsey-County, Minnesota	Minnesota	Sales Clerk	Daughter
1940	Mary Hennessy	29	Baltimore-City-County, Maryland	Maryland	Salesgirl	Daughter
1930	Mary Hennessy		Cook, Illinois	Ireland	—	Wife
1920	Mary Hennessy		Oklahoma, Oklahoma	Illinois	None	Head
1920	Mary Hennessy		Philadelphia, Pennsylvania	Ireland	—	Head
1920	Mary Hennessy		Kings, New York	Ireland	None	Head
1940	Mary Hennessy	64	Bronx-County, New York	Ireland	Laundress	Head
1930	Mary Hennessy		Androscoggin, Maine	Maine	Inspector	Daughter
1930	Mary Hennessy		Suffolk, Massachusetts	New Jersey	—	Wife
1910	Mary Hennessy		Norfolk, Massachusetts	England	—	Wife
1910	Mary Hennessy		Middlesex, Massachusetts	Ireland	None	Wife
1930	Mary Hennessy		Blue Earth, Minnesota	Minnesota	—	Daughter
1930	Mary Hennessy		Hampden, Massachusetts	Massachusetts	None	Daughter
1910	Mary Hennessy		Rice, Minnesota	New York	—	Wife
1900	Mary Hennessy	47	Kings, New York	Ireland	—	Wife
1940	Mary E. Hennessy	15	Fayette-County, Pennsylvania	Pennsylvania	—	Daughter
1930	Mary Hennessy		Cook, Illinois	Michigan	—	Wife
1900	Mary Hennessy	57	Providence, Rhode Island	Ireland	—	Wife
1930	Mary L Hennessy		Hamilton, Ohio	Ohio	—	Daughter
1940	Mary Hennessy	45	Suffolk-County, Massachusetts	Irish Free State	Chauffeur	Wife
1940	Mary Louise Hennessy	24	Hamilton-County, Ohio	Ohio	—	Daughter
1920	Mary E. Hennessy		Providence, Rhode Island	Rhode Island	—	Daughter
1930	Mary J. Hennessy		Suffolk, Massachusetts	Irish Free State	—	Wife
1940	Mary Hennessy	16	Richland-County, Wisconsin	Wisconsin	—	Daughter
1910	Mary Hennessy		Schuylkill, Pennsylvania	Ireland	House Keeper	Head
1940	Mary Hennessy	18	Wayne-County, Michigan	Michigan	New Worker	Daughter
1940	Mary Hennessy	13	Suffolk-County, Massachusetts	Massachusetts	—	Daughter
1930	Mary Hennessy		Kings, New York	New York	None	Daughter
1940	Mary Hennessy	56	New-York-County, New York	New York	—	Wife
1940	Mary Hennessy	44	New-York-County, New York	New York	—	Wife

Load More Mary Hennessy Census Records

About Mary Hennessy US Census Records & Model Tree

We've indexed 2731 free, proprietary US Census records for Mary Hennessy across 1900–1950, covering 46 states and DC: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, District of Columbia, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming.

Each record includes our Model Tree — a longitudinal reconstruction that links the same person across census decades using machine learning (XGBoost record linkage). Every link carries a confidence score: Verified (≥0.99), Confirmed (≥0.95), or Linked (lower confidence). This tells you not just what the census says, but how reliably we've connected records across time.

Every record also shows the full household — who Mary lived with, their ages, birthplaces, and occupations. For 1940 and 1950 records, you can view the original handwritten census page from the National Archives.

How we build the Model Tree. YourRoots independently indexes US Census records from NARA microfilm and links persons across decades using XGBoost-based record linkage. Each link's confidence is a per-pair match score from the model. Household corroboration (co-residents appearing on the same census pages in multiple years) strengthens the signal. The Model Tree is not a family tree submitted by users — it's reconstructed from the census data itself.

Last updated: July 30, 2026

Frequently Asked Questions

: We have 2731 US Census records for Mary Hennessy, from 1900 to 1950, across 46 states and DC.
: You'll see Mary's age, birthplace, occupation, and relationship to the head of household — plus everyone else who lived in the same home. For 1940 and 1950 records, you can also view the original handwritten census page.
: Census records are a snapshot of a family every 10 years. You can follow Mary Hennessy's household over time — see when children appear, when people move states, and who's living together. YourRoots connects census data with Tree Matching and AI tools so you can build out your tree faster.
: Yes. All Mary Hennessy census records on YourRoots are free to search and view — no subscription required. We built our own index from the original federal census images.
: We have Mary Hennessy records from the 1900 through 1950 US Federal Census, across 46 states and DC. Use the year and state filters above to narrow your results.
: Start by narrowing the year and state. If you know an approximate birth year, use the age column to match — census age minus the census year gives you a birth year estimate. Household members, birthplace, and occupation help confirm you have the right person.
: The Model Tree is YourRoots' unique feature that links a person across multiple census decades and reconstructs their likely family — parents, siblings, spouse, and children — based on household patterns. It turns isolated records into a connected family network.
: All records originate from the US Federal Census microfilm digitized by NARA (National Archives and Records Administration). YourRoots re-indexed the original page images using modern AI, catching names and details that older transcriptions missed.

Other Hennessy US Census Records

All Hennessy census records →

Browse More Surnames

Heath Heller Henderson Hendricks Hendrickson Hennessey Henry Henson Herbert Herman Hernandez Hess

← Back to US Census Records