The majority of this collection consists of correspondence between Samuel Miller and eminent clergymen in America, England, and Scotland. His exchanges with such men as Gardiner Spring, Benjamin Wisner, and Ashbel Green show not only immense piety but also a deep interest and concern for matters pertaining to Presbyterians, as well as Christendom, of his time. Moreover, as evident from his correspondence with contemporaries like George Washington, John Adams, Thomas Jefferson, and John Jay, Miller was also quite involved in the political atmosphere of America's emerging republic. Letters from Joseph Brant, a Native American Christian proselytizer, foreign missionaries, such as William Carey, and foreign correspondents, such as Christopher Daniel Ebeling of Hamburg and Samuel Miller of Scotland, are testaments to Miller's attentiveness to Christians and non-Christians in America and around the world.

The collection also contains legal documents, manuscripts, diary entries, and other letters pertaining to Miller's daily life as a son, brother, husband, father, professor, and friend. There is much correspondence pertaining to Princeton Theological Seminary and Miller's initial acceptance of a position, his struggles with finances at the Seminary, his eventual reputation as a professor and authority on theological issues, and his final attempts to retire from his duties towards the end of his life. In fact, because the contents of the collection span such a large range of dates, they provide a fairly full picture of Miller's life. In addtion, there are letters to Miller's father, Rev. John Miller, his son, Samuel Miller, Jr., and his wife, Mrs. Sarah Miller. Of these letters, the ones written during Miller's life provide an even broader image of his and his family's interests. Those written before his birth provide a valuable glimpse at the environment in which he grew up, and those written after his death speak to Miller's influential life and the thoughts, feelings, lives, plans, and futures of his family and friends without him.