The collection consists of manuscripts, correspondence, documents, and photographs concerning the Throop and Throop Martin families of New Jersey, primarily represented by Enos Thompson Throop, governor of New York (1830-1833), and E. T. Throop Martin, Governor Throop's nephew and secretary. Family correspondents include Francis Preston Blair (1848-1877), Montgomery Blair, Blair Lee, Elizabeth Blair Lee, Eveline Martin Alexander, and Emory Upton (1868-1879). There are also three folders of correspondence (1829-1862) between Martin Van Buren and Enos Thompson Throop, as well as Emily Martin Upton's letterbook (1868-1869) and diary (1858-1867), a copy of Eveline Martin Alexander's diary (1867), Cornelia Martin's diaries (1847-1849), and Nelly Martin's account books (1893-1912) for her pickle and preserve business.

In addition to the family correspondence, there is an autograph collection containing letters of, among others, Elias Boudinot, Aaron Burr, Rufus Choate, Charles Dickens, Benjamin Franklin, the Marquis de Lafayette, Samuel Miller, Jedidiah Morse, Thomas Paine, Sarah Payson Parton, Anne Louise Stael, John Trumbull, Daniel Webster, and Eli Whitney. Other items include the will of Enos Thompson Throop, 17th- and 18th-century legal documents, two pieces of Confederate money, a tally of the Electoral College of New York State from the election of 1844, the diplomatic agreement on etiquette for members of the Diplomatic Corps decided at the Naples convention in 1839, a biographical sketch of Francis Preston Blair, and stock certificates.