Abstract: On September 21, 1638, the Mohegans, the Narragansetts, and the English colonists on the Connecticut River reached an agreement at Hartford to settle their affairs following the Pequot War. The original copy of the treaty having been lost, scholars have depended almost exclusively on a copy prepared for the 1705 hearing of the Mohegan land case. However, this document represents only a fragment of the original agreement, leaving out four of the thirteen provisions agreed to by the parties in 1638. The original text of the treaty is reconstructed here by drawing on all of the surviving copies of the agreement: the 1705 copy already familiar to historians, a 1734 copy prepared during a later hearing of the Mohegan land case, and a newly rediscovered copy dating from 1665 and held among the British Library’s Lansdowne Manuscripts. This reconstructed treaty illuminates how indigenous polities and English settlers sought to navigate the jurisdictional politics of early America. Moreover, it presents scholars with an important resource for reconsidering the evolution of Anglo-Indian relations in New England, particularly the breakdown of the relationship between the Massachusetts Bay Colony and the Narragansetts in the early 1640s.