This index results from a partnership between the Balch Institute Center for Immigration Research and the John F. Kennedy Trust of Wexford County, Ireland. Both organizations worked together to choose, organize, and present the information. The data for the index comes from ship manifest schedules kept at the National Immigration Archives in Philadelphia.
The National Immigration Archives is a goldmine for anyone interested in European immigration history, as it holds one of the largest collections of such data in the Western Hemisphere. Specifically, it maintained U.S. passenger lists from 1820 until just before World War I. So, if you’re looking for comprehensive immigration data, this index, backed by an extensive archive, could be a great resource.