These letters are alphabetically arranged, and then chronologically within each group. There are some pieces concerning the Cabells and their kin, but most of these letters bear on Brown's most substantial work, "The Genesis of the United States." Correspondence with Houghton Mifflin (his publisher) is well-represented. A minority of pieces bear on Brown's personal business transactions, chiefly real estate. However, this section contains little of a personal nature; there are no letters from either of his wives and such letters that come to him from relatives seem to have been inspired by Brown's request for data of the family.

These letters contain notes and records by Brown or one of his correspondents and letters supplying data for the Cabells and Their Kin. The folders are arranged alphabetically by the name of the family.

This section differs from the preceeding series in that it comes in the form of notes, transcripts, and drafts; there is no correspondence as such. For convenience, these groups were divided into Genesis, Documents, and Miscellany. Genesis contains copies of records of the London and Virginia Companies. Miscellany contains clippings, envelopes, miscellaneous letters and notes, and imprints.