The major part of this work is an alphabetically arranged and cross-indexed list of some 20,000 Maryland families with references to the sources and locations of the records in which they appear. In addition, there is a research record guide arranged by county and type of record, and it identifies all genealogical manuscripts, books, and articles known to exist up to 1940, when this book was first published. Included are church and county courthouse records, deeds, marriages, rent rolls, wills, land records, tombstone inscriptions, censuses, directories, and other data sources.