You've got family at Ancestry.

Find more Obrien relatives and grow your tree by exploring billions of historical records. Taken every decade since 1790, the U.S. Federal Census can tell you a lot about your family. For example, from 1930 to 1940 there were 3,290 more people named Obrien in the United States — and some of them are likely related to you.

Start a tree and connect with your family.


Create, build, and explore your family tree.

What if you had a window into the history of your family? With historical records, you do. From home life to career, records help bring your relatives' experiences into focus. There were 23,749 people named Obrien in the 1930 U.S. Census. In 1940, there were 14% more people named Obrien in the United States. What was life like for them?

Picture the past for your ancestors.

In 1940, 27,039 people named Obrien were living in the United States. In a snapshot:

  • 1% reported their race as other than white
  • The average annual income was $1,215
  • 2,750 owned their homes, valued on average at $4,262
  • 1,236 were disabled

Learn where they came from and where they went.

As Obrien families continued to grow, they left more tracks on the map:

  • 8,546 were first-generation Americans
  • 13% were born in foreign countries
  • 3,126 were born in foreign countries
  • The most common mother tongue was Gaelic