What the National Archives holds and how it connects to your family tree
The National Archives is a federal repository in Washington, D.C., that preserves original government documents going back to 1776. For genealogy research, the most useful records are census data, military service files, naturalization papers, and passenger ship manifests — all of which contain names, dates, places, and family relationships that help you trace ancestors.
The National Archives does not hold every record about every person. State and local governments keep birth certificates, marriage licenses, and death records. The National Archives focuses on federal records: who served in the military, who immigrated through federal ports, who was counted in the decennial census, and who went through federal naturalization courts. If your ancestor crossed a border, wore a uniform, or became a citizen, there is likely a federal record.
You can search some of these records free online through the National Archives website without visiting in person. Other records require a trip to Washington, D.C., or a request by mail or through a research service. Understanding which records exist and where they live saves you time and money.
Key Takeaways
- The National Archives holds census records, military files, naturalization documents, and ship manifests — the four most useful sources for genealogy research.
- You can search digitized census records and some military indexes free on the National Archives website; other records require an in-person visit or a formal records request.
- Passenger ship manifests from 1820 onward are searchable online and show the ship name, arrival date, and the names of everyone aboard, including family members traveling together.
- Military service records exist for every branch and every war; finding the correct regiment or unit number speeds up your search significantly.
- Naturalization records held at the National Archives are limited to cases filed in federal court; most naturalization happened in state and local courts instead.
Census records: the backbone of genealogy research
The decennial census — taken every ten years since 1790 — is the single most useful record for tracing a family line. Each census lists the head of household by name, the names of everyone living in that household, their ages, birthplaces, and occupations. The 1930 census and earlier are open to the public; the 1940 census became available in 2012, and each subsequent census opens 72 years after it was taken.
You can search the 1790 through 1940 censuses free on the National Archives website. The search tool lets you enter a name, approximate year, and state. Results show the census page image and a transcription. Census records are not always accurate — names were spelled phonetically by enumerators, ages varied by a few years, and birthplaces were sometimes guessed — so search multiple census years and compare the results.
If you find an ancestor in the 1930 census, you can work backward through 1920, 1910, and earlier censuses to watch the family move, grow, and change. Each census also lists the state or country where each person was born, which tells you where to search next for birth records or immigration documents.
Military records: service files and pension applications
If your ancestor served in the U.S. military, the National Archives holds a service record and possibly a pension file. Service records contain the soldier's name, rank, unit, dates of service, and sometimes notes about wounds or discharge. Pension files — applications for benefits after service ended — often include family information, marriage certificates, and letters from relatives proving dependents.
The National Archives website has a searchable index of soldiers from the Revolutionary War through World War I. You can search by name and state. If you find a match, you can order the full service file by mail or through a research service. The file itself is not digitized online, but the index tells you whether a record exists and gives you the reference number to request it.
For World War II and later conflicts, service records are held by the National Personnel Records Center in St. Louis, not the National Archives. The National Archives website has links to that office and instructions for requesting records. Knowing which branch your ancestor served in — Army, Navy, Marines, Coast Guard, or Air Force — helps narrow the search, because each branch kept separate records.
Passenger ship manifests: arrival records with full family names
If your ancestor immigrated to the United States, a passenger ship manifest recorded their arrival. These manifests list every person aboard, their age, occupation, last residence, destination in America, and the name of a relative or friend already in the country. Manifests from 1820 onward are searchable free on the National Archives website through a tool called "Passenger Search."
The search works by entering a passenger name, approximate arrival year, and the port of arrival. Major ports were New York, Boston, Baltimore, Philadelphia, and New Orleans, though immigrants arrived at many smaller ports too. Results show the ship name, arrival date, and a link to the manifest page image. The manifest shows not just your ancestor but everyone traveling with them — spouses, children, siblings — which helps you understand family structure at the moment of arrival.
Manifests do not always spell names consistently, and handwriting can be hard to read, so try variations of your ancestor's name and search a range of years. Once you find a manifest, note the ship name and arrival date; these details help you search for naturalization records filed shortly after arrival, since many immigrants became citizens within a few years of landing.
Naturalization records: citizenship documents and court files
Naturalization — the legal process of becoming a U.S. citizen — created two types of documents: a declaration of intention (filed first) and a naturalization certificate (filed after a waiting period and a court hearing). The National Archives holds naturalization records filed in federal courts, but most naturalization happened in state and local courts instead, so the records you need may not be at the National Archives.
The National Archives website has a searchable index of naturalization records from federal courts. You can search by name and approximate year. If you find a record, you can order it by mail. The document shows the person's name, the date of naturalization, the country of origin, and sometimes the date of arrival in America — information that connects to ship manifests and military records.
If you do not find a record in the federal index, contact the state or county courthouse where your ancestor lived. Most naturalization happened there, and those records are kept locally. The National Archives website has a guide to finding state and local naturalization records, with links to state archives and courthouse websites.
How to search the National Archives website and order records
The National Archives website (archives.gov) has several search tools organized by record type. The main genealogy tools are the Census Search, Passenger Search, Military Index, and Naturalization Index. Each tool works slightly differently, but all are free to use.
Start with the record type most likely to contain your ancestor. If you know they immigrated, search the Passenger Search first. If you know they served in the military, search the Military Index. If you only know they lived in America, start with the Census Search and work backward through decades to build a timeline.
When you find a record online, you can view the image for free. If you need an official copy — a certified document to use for genealogy research or legal purposes — you can order it through the National Archives website. Orders are processed by mail and take several weeks. The cost varies by record type, typically between $10 and $30 per document. Some records can be ordered through third-party research services, which charge a fee but may be faster.
Visiting the National Archives in person or requesting records by mail
The National Archives building in Washington, D.C., has a research room where you can view original documents and microfilm. You do not need an appointment for the reading room, but you do need a free researcher ID card, which you can obtain on the day of your visit. The reading room is open Monday through Friday, and staff can help you locate records and use the microfilm readers.
If you cannot visit in person, you can request records by mail. The National Archives website has a form for ordering records by mail. You provide the record type, the person's name, and any reference numbers you have from your online search. Processing takes several weeks, and you pay a fee per document.
You can also hire a professional researcher through the National Archives website. These researchers work on-site and can search records on your behalf. This option costs more but is useful if you need many records or if you are not sure which documents to request.
Frequently Asked Questions
Can I search the National Archives online for free?
Yes. Census records from 1790 to 1940, passenger ship manifests from 1820 onward, military indexes, and naturalization indexes are all searchable free on the National Archives website. You can view the images of most records online at no cost. If you want an official certified copy, there is a fee.
What if I cannot find my ancestor in the census?
Census records are not complete. People were missed, names were misspelled, and some records were damaged or lost. Try searching with variations of the name, search multiple census years, and search neighboring states. If your ancestor was in an institution — a military barracks, a prison, a hospital, or a boarding school — they may appear in a separate institutional census rather than a household census.
How do I know which military branch my ancestor served in?
Start with the Military Index on the National Archives website and search by name. The index results show the branch and unit. If you do not find them there, try searching state military records or pension records, which sometimes list the branch. Local historical societies and veterans' organizations can also help identify which unit your ancestor served in.
Are naturalization records at the National Archives the only ones that exist?
No. The National Archives holds naturalization records filed in federal courts, but most naturalization happened in state and local courts. If you do not find a record in the federal index, contact the courthouse in the county where your ancestor lived. State archives websites usually have guides to finding naturalization records in that state.
How long does it take to get records ordered by mail?
Processing typically takes several weeks to two months, depending on the volume of requests. Expedited processing is sometimes available for an additional fee. Check the National Archives website for current processing times before you order.