PROVO — Between 1820 and 1960, more than 41 million people boarded ships to start new lives as American immigrants.

Now, information about those new Americans and millions of other travelers to the United States during that time is being made available in a searchable index by Provo-based Ancestry.com.

The collection of all readily available U.S. passenger lists for that period is being launched on the Web site today, allowing people to glean details about ancestors from the more than 100 million names in the searchable index and the approximately 7 million images of the actual lists.

"This passenger list collection is one of most emotional and accessible collections we've ever put online," said Tim Sullivan, chief executive officer of MyFamily.com Inc., the parent company of Ancestry.com.

"It's tremendously exciting to us as a company, but on a personal level, as the great-grandson of a whole lot of ancestors who actually passed through these ports, it's tremendously satisfying. The impact to me and anyone who will browse this collection of seeing the name of an ancestor on a passenger list on the day they entered this country as a new citizen is incredibly powerful and important."

Ancestry.com says 250 million people in the United States can trace their lineage to at least one listed immigrant. "Eighty-five percent, like me, have at least one ancestor included in this passenger list collection," Sullivan said.

Ship crews created the lists following an 1819 law requiring U.S.-bound vessels to record passenger information. The Ancestry.com collection includes details about travelers to more than 120 U.S. ports of arrival, including the entire collection of passenger list records from Ellis Island. For example, an ancestor of Martha Stewart is recorded on the S.S. Iceland manifest as a "basket maker."

Sullivan hailed the online collection as a single source for the records, which previously could only be found at the ports, on microfilm at libraries and museums, or, on a limited basis, at other Web sites.

"We're happy that people have places to go (online) to see bits and pieces, but we're excited that we're the one place that has the entire collection of all the readily accessible lists of that entire 140 years that kind of defines the great era of immigration into the United States," he said.

Users would benefit by first checking with other family members about family history and then building a family tree at Ancestry.com, he said. The company's systems then can search through its more than 5 billion names and 23,000 searchable databases to find possible ancestor matches.