Series 1, arranged chronologically, consists of letters from Benjamin Tallmadge to George Washington during the American Revolution, and letters among Tallmadge's family members after the war. The letters are fair copies in Tallmadge's hand.

Tallmadge's letters to Washington document his military activities, as well as his activities as George Washington's chief intelligence officer and the organizer of the Culper spy ring. The collection also contains two original letters from George Washington to Tallmadge (in folders 12 and 18).

After the war, Tallmadge's correspondence with his family members record his business activities as well as religious, political, and social news in Litchfield, New England, and Washington, D. C.