BOSTON: Just in time for St. Patrick's Day, genealogical research website Ancestry.com is making 10 million Catholic parish records from Ireland — some dating to 1655 — available online for free to help people trace their Irish heritage.

The goldmine of information, available without cost for a week starting Friday, includes baptism, confirmation, marriage, and burial records from more than 1,000 parishes in both the Republic of Ireland and Northern Ireland.

"This will really help people reconstruct their family story," said Lisa Elzey, a family historian at Ancestry, which now offers access to 55 million Irish records. "There's all kinds of mysteries within these records."

More than 33 million Americans claimed Irish ancestry in 2014, according to the latest US Census data, or about 10 percent of the nation's population.

The documents, usually in English but sometimes in Latin, and dating from 1655 to 1915, had already been digitised by the National Library of Ireland, but Ancestry took the information and indexed it, making it possible to do much quicker and more efficient searches using names, places and dates.

The trove contains information on prominent Irish citizens as well as the forebears of famous Irish-Americans.

Included is the 1828 marriage record, in Latin, of President John F. Kennedy's great-great-grandparents: Edmundus FitzGerald and Maria Lenihan.

The records also include baptism records of author James Joyce and Irish-born White House designer James Hoban.

They tell not only the stories of Irish families, but help explain the cultural and religious fabric of the island, said the Rev. Oliver Rafferty, a professor of history and Director of Irish Programs at Boston College.

The older records in particular, he said, are fragmented.

"There are enormous gaps in Catholic records, especially the older ones, much of it because of the periodic persecution of Catholics at various stages of Irish history," he said.

The records from parishes in the towns tend to be more complete that those from churches in remote rural areas, said Rafferty, who is familiar with the records because of their availability from the national library.

Perusing the documents can help researchers make connections through maiden names, godparents' names, and marriage witnesses' names.

"It's absolutely key to look at things like witnesses and to study the people around a family in order to build context and the bigger picture," said Michal Brophy, a Massachusetts-based member of the Association of Professional Genealogists, who says Irish-American research is one of his specialties.

"This will be exciting to see," he said.