Making Nations: The Northeastern Borderlands in an Age of Revolution, 1760-1820 examines migration within northeastern North America, and the gradual formation of a meaningful border between the District of Maine and the Province of New Brunswick. The American Revolution, though it divided the northeast between New England and British North America, did not fundamentally change attitudes toward the borderland. For decades, the region had been a special sort of frontier – a more connected frontier, offering migrants from southern New England better access to Atlantic trade. The post-revolutionary era rapidly reverted to pre-war patterns, as settlers crossed a largely meaningless border looking for fertile land and economic connectivity. These settlers, I argue, were not late loyalists, choosing British territory, or early republicans, choosing the U.S. This was one migration, to the borderland and the similar opportunities on both sides. So how did migration within a shared borderland become immigration across a meaningful border? Post-revolution, both Congregationalists and Catholics began to build networks in Maine that stopped at the border. A Congregational missionary society, the Society for Propagating the Gospel Among the Indians and Others in North America, realized it could secure state funding from Massachusetts by advertising itself as a tool for managing the growing settlements in Maine. State money helped the society grow rapidly, and as similar groups formed they chose to join the pioneer society as partners rather than compete with it. Meanwhile, Congregational women created institutions called “ladies cent societies,” which provided a massive infusion of funding into the system. The resulting Congregational network grew to encompass almost the entire American half of the borderland. At the same time, a Catholic network also grew in Maine, connecting the Catholic Passamaquoddy and Penobscot people to Boston, as well as to Irish Catholics along Maine’s coast. As these networks grew they changed eastern Maine from a place that was attractive because of its connections with British North America, to a place that was attractive because of its connections with New England. These networks made the border meaningful – and immovable. Though politicians on both sides persisted for years in believing they could still adjust the border, they were wrong. It had already taken root.