Taking over 10 years of research by his cousin, Amos Lowell, Delmar spent nearly 15 more years researching and documenting the history of Lowell family in America starting with the founding patriarch in America, Percival Lowle (1571—1664). Delmar's effort culminated in the 2 volume publication The Historic Genealogy of the Lowells of America from 1639 to 1899.

In the preface, Lowell notes that another descendant, Judge James H. Lowell, (Vol 1, p. 197) a native of Boston who eventually settled in Holton, Kansas (1842-1925), wrote the transatlantic history of the family contained in the genealogy, from Percival's emigration from England backward for nine generations: "We call special attention to this chapter as a most valuable part of this work." The chapter James Howard Lowell wrote is Chapter III, entitled, Transatlantic Ancestry of the American Lowells, pp. xxxiv - xlix. James Howard Lowell contributed much of the research on the coats of arms as well.

After more than two decades, Lowell documented the births, birthplaces, marriages, remarriages, children, and the deaths of Lowells all over the United States from 1639 to 1899. His 2 volume book runs 826 pages and covers literally thousands of his kinsmen living and dead. The contents of several early wills, including John, Richard, and Percival's, are included in his publication. Lowell also went to great lengths in researching the family Coat of Arms and the evolution of his surname.

Lowell's work, coupled with Ferris Greenslet's biography, The Lowells and Their Seven Worlds,^[2] are considered two of the primary resources for most modern researchers looking into the Lowell family history. Much of Lowell's research on Percival Lowle's ancestry can be found today copied in the online genealogies of hundreds of families who have traced their own American heritage to founding the Lowell's.

• Lowell family

• The Historic Genealogy of the Lowells of America from 1639 to 1899, Delmar R. Lowell, The Tuttle Company, Printers, Rutland, Vt., 1899
• ISBNdb.com