Series I. Professional Activities represents the surviving evidence of Phillips' work as historian and collector. Papers attributed to Phillips and others (B1 F1) are mostly associated with the history and culture of Hawaii, with particular emphasis upon the activities of Captain James Cook. Other important items include a complete set of page proofs from the exhibition catalog The Hawaiian Portion of the Polynesian Collections in the Peabody Museum of Salem (1920) and research notes concerning voyages of the ship Wager from 1740-1746 (B1 F3).

Subseries B. Correspondence contains letters to Phillips as well as outgoing letters. The majority of the correspondence was received from book collectors, historians, and curators. Of particular interest are letters from Clarence Brigham (American Antiquarian Society), Worthington C. Ford (Massachusetts Historical Society), and Lawrence C. Jenkins (Peabody Museum of Salem). An enclosure in the Jenkins correspondence and a letter from an unidentified "Miss Allen" provide interesting insights into Hawaiian culture.

Subseries C. Diaries contains three volumes of diaries or day books.

Subseries D. Financial consists of various personal financial papers.

Subseries E. Printed Matter consists of a variety of ephemeral printed items. News clippings include a eulogy of Stephen Henry Philips [father] and notice of the opening of the Haverhill Historical Society's building, "The Buttonwoods", in 1904. This series also contains Phillips' Certificate of Naturalization, an exhibition poster of the ship Recovery of Salem, and a Merchants National Bank calendar with illustrations of historic houses in Salem (B15 F2).