The democratic and territorial peace arguments explain interstate peace via distinct mechanisms. Yet they can be integrated. I theoretically derive both the unique domains in which each argument might operate and the ways in which the two arguments might reinforce one another. An analysis of the period 1816–2001 demonstrates support for a more integrative approach. Within contiguous dyads, border settlement significantly reduces conflict, even for non-democratic dyads. Democratic dyads, however, experience no such effect in the absence of border settlement. Nonetheless, the democratic peace functions strongly in non-contiguous dyads, and even the most peaceful, contiguous dyads require both democracy and border settlement. Such findings offer a foundation for further theoretical development that integrates the two arguments.