Until now, the bureau's trove has been accessible only to those who go in person to the National Archives in Washington, or look online in the difficult-to-search pages of microfilm at familysearch.org, the genealogical history website of the Church of Jesus Christ of Latter-day Saints. Representatives of the denomination, a sponsor of the indexing project, and local genealogists will hold an information session on the effort Thursday at 7 p.m. at the African American Museum in Philadelphia.