"It's a very big deal," said Fran Bumann, who volunteers with genealogy organizations in Southern California.

U.S. law states that at least 72 years must pass before data collected in a census can be released. Some countries have to wait much longer. In the U.K., for example, the most recent publicly available census is from 1911.

Bumann said she and her colleagues get incredibly excited beforeeach census is released and hope the 1940 census will fill gaps in their family trees. The best part of being an amateurgenealogist, she said, is how easy the Internet has made information-gathering.

"When I started, I would write letters and wait months to hear back, I had to go to the library just to leaf through pages. I probably sound ancient to you, but you had to take notes by hand," Bumann, 72, said. "The Internet has just made things explode."

With more than 8 billion online records, Ancestry.com is one of the major sites in the genealogy research subscription realm. The business is trying to hire 150 new employees this year, most of them engineers. It's also unveiling new features on its site, like an integrated Facebook Connect feature and software that aims to makecensus forms easier to read.