Tracing your bloodline starts with what you already know and works backward through a combination of family records, public documents, DNA testing, and online databases. Most people can reliably trace their lineage back four to six generations using paper records alone, and DNA testing can extend that reach or fill in gaps where documents don’t exist. The process takes patience, but the tools available today are more powerful and accessible than at any point in history.
Start With What Your Family Already Knows
Before you open a database or order a DNA kit, interview your oldest living relatives. Ask for full names (including maiden names), birth and death dates, places of residence, occupations, and any stories about where the family came from. Write down details that seem minor: the name of a town, a church, or a family business. These fragments become search terms later.
Gather physical documents if you can. Birth certificates, marriage licenses, old photographs with names written on the back, family Bibles with records pages, funeral programs, and naturalization papers are all primary sources. Even an old envelope with a return address can point you toward a census record or city directory that unlocks the next generation back.
Use Online Genealogy Databases
Three major platforms hold the bulk of digitized genealogical records, and each has different strengths.
- Ancestry.com holds more than 60 billion records (including user-submitted family trees) and is especially strong for U.S. research. It requires a paid subscription but offers the largest searchable collection of American vital records, census data, and immigration documents.
- FamilySearch is completely free and run by the Church of Jesus Christ of Latter-day Saints. It reports 14.7 billion searchable name records, with browse-only image collections that could push the total as high as 66 billion. It covers roughly 200 countries, making it the most geographically diverse option.
- MyHeritage catalogs more than 32 billion records and is particularly strong for UK, European, and Jewish genealogy, with deep collections for France, Germany, Greece, Ireland, the Netherlands, Scandinavia, and Spain.
Start by building a basic family tree on one of these platforms. As you add names and dates, the system will suggest matching records: census entries, draft registrations, passenger lists, and more. Cross-reference what you find across multiple platforms, since each has records the others don’t.
Census, Immigration, and Military Records
U.S. Census records are available from 1790 through 1950. A 72-year privacy restriction keeps more recent census data sealed, so 1950 is currently the newest year you can access. Census records list household members by name, age, birthplace, occupation, and relationship to the head of household. Tracing the same family across multiple census decades can reveal migration patterns, changing family structures, and clues about earlier generations.
If your ancestors immigrated to the United States, passenger arrival records (ship manifests) are one of the richest sources available. These documents often include nationality, place of birth, age, physical description, profession, last place of residence, the name and address of the relative they were joining in the U.S., and even how much money they were carrying. The National Archives holds these records, and many are searchable through Ancestry and FamilySearch.
Military service records can fill in biographical details that don’t appear anywhere else. Personnel files become open to the public 62 years after a veteran leaves the military. Anyone can order a complete copy of an Official Military Personnel File from the National Personnel Records Center in St. Louis. You’ll need the veteran’s full name, branch of service, and approximate dates of service. A file of six pages or more costs a flat $70. If your ancestor served before 1912, be aware that a 1973 fire at the records center destroyed millions of Army and Air Force files, so some records may not survive.
How DNA Testing Works for Lineage
DNA testing picks up where paper records leave off, and it can confirm (or surprise you about) what the documents say. There are three types of tests, each tracing a different line.
Autosomal DNA is what most consumer tests from 23andMe, AncestryDNA, and MyHeritage analyze. It examines the 22 pairs of non-sex chromosomes you inherited from both parents. This test estimates your ethnic mix and matches you with living relatives who share DNA segments. Its practical range is about five to seven generations, because the amount of DNA you inherit from any one ancestor drops by half with each generation. By the time you go back six generations to your great-great-great-great-grandparents, you share only about 1.56% of your DNA with each of them, and it’s possible to carry no detectable DNA from a specific ancestor at that distance.
Y-DNA testing traces the direct paternal line: father to father to father. Only people with a Y chromosome can take this test. Because the Y chromosome passes relatively unchanged across many generations, it can trace a surname line back hundreds or even thousands of years and connect you with distant paternal relatives.
Mitochondrial DNA (mtDNA) testing traces the direct maternal line: mother to mother to mother. Everyone inherits mtDNA from their mother, but only women pass it on. Like Y-DNA, it mutates slowly and can reach deep into the past, though it follows only one narrow line through your tree.
Making Sense of DNA Matches
When your results come back, you’ll see a list of genetic matches ranked by how much DNA you share, measured in units called centimorgans (cM). The more centimorgans you share with someone, the closer your relationship. But the same amount of shared DNA can point to several possible relationships. A match in the range of 575 to 1,330 cM, for instance, could be a first cousin, a half aunt or uncle, or even a grandparent. Context from your family tree is what narrows it down.
The real power of DNA matching is connecting with living relatives who may have pieces of the puzzle you’re missing: old photos, family stories, or records from a branch of the family you didn’t know existed. Reach out to your closest matches and compare notes.
Research the Community, Not Just the Person
When you hit a dead end on a specific ancestor, widen your focus. Professional genealogists use what’s called the FAN principle, which stands for Friends, Associates, and Neighbors. The idea is simple: your ancestors didn’t live in isolation. They witnessed each other’s marriages, co-signed land deeds, served in the same military units, and lived on the same streets.
Think of it like ripples on a pond. Your target ancestor is the center. The first ring is their immediate family. The next ring includes people with the same surname in the area, then neighbors listed on the same census page, then business partners or fellow church members. When your ancestor left no record that answers your question directly, someone in their circle often did. A neighbor’s obituary might name the town in the old country. A business partner’s naturalization file might list the same village of origin. These indirect discoveries are often how the toughest brick walls get broken down.
Privacy Considerations for DNA Testing
Before you spit in a tube, it’s worth understanding what happens to your genetic data. The United States has no comprehensive federal privacy law covering consumer DNA. HIPAA, the health privacy law most people have heard of, applies to healthcare providers and insurers but generally does not cover direct-to-consumer genetic testing companies. A minority of states have enacted genetic privacy laws that require companies to get your express consent before sharing your data with third parties, but protections vary widely by state.
The 2024-2025 bankruptcy of 23andMe brought these risks into sharp focus. Twenty-eight states attempted to block the sale of the company’s genetic database, arguing that privacy laws should prevent the transfer of customer DNA data without individual consent. Law enforcement agencies have also accessed consumer DNA platforms to identify suspects. The 2018 arrest of the Golden State Killer came after investigators uploaded crime scene DNA to a genealogy platform and built a family tree that led to the suspect. Since then, law enforcement has pursued suspects in hundreds of cases using similar techniques. Larger companies like 23andMe and Ancestry have publicly committed to resisting law enforcement access, but smaller platforms that allow third-party DNA uploads have proven more vulnerable.
If privacy concerns you, read the terms of service before testing. Look for companies that let you download your raw data, delete your account and sample, and opt out of research programs. Some people choose to upload results only to platforms where they can control visibility settings and limit who can see their profile.