The Moses Warren, Jr., letters contain 12 letters written by Warren to his wife, Mehitabel, in 1796-1797, with a gap from August 1796 to March 1797. Warren wrote the first letter while onboard the Lark on May 4, 1796, and the rest while traveling around upstate New York and eastern Ohio with a group of surveyors for the Connecticut Land Company. In his correspondence, he described his work and colleagues, interactions with Native Americans, and the difficulties of surveying, including bad weather and illness.
In several of his letters, Warren made observations about Native Americans. On July 9, 1796, he recounted signing a treaty and smoking a peace pipe with Prince Cato and the Missisago Indians at "Port Independence." In the same letter, he also listed the gifts exchanged, and compared the Missisago language to that of the Mohegan. While in Youngstown, Ohio, he noted the scarcity of Native Americans, whom he believed were avoiding his party out of fear, and described the initial wariness of the "Tawa" (Ottawa) men (July 31, 1797).
In other correspondence, he described the men of his party, who were "very active & well informed, except 3 or 4" (May 8, 1797), and gave details about their health and tasks. Of his own work, he noted an assignment to "run the 5th East & West line to Pennsylvania" (June 18, 1797). At times, weather and accidents interfered with the group's progress: a "deluge" of rain near Buffalo Creek in New York caused delays (May 25, 1797) and a man drowned while accompanying a horse across a river (June 18, 1797). Warren also frequently described illnesses, such as dysentery and ague, which struck many of them while traveling.