My sense that expansion has been framed as a coming of age story is tied to the way historians have periodized it. Historians, of course, write backward from their present, so there was some logic to Frederick Jackson Turner writing in 1893 that the United States had achieved its territorial limits and was in effect all grown up. The problem is the United States continued to grow, and yet historians didn’t change their narrative. The United States would go on to acquire more territory, but these now would be as children—tied to the paternal imperial nation, but not fully part of its body.[3] Expansion was the story of the growth of the national geobody; empire was the story of the incorporation of subordinate territories. For decades, historians have emphasized that the United States’ nineteenth-century expansion was in fact imperial. And yet the term “expansion” remains temporally bound by the nineteenth century and geographically confined to contiguous territory. As a result, we’re left with a national narrative that only awkwardly includes Alaska and Hawai’i despite their statehood, let alone U.S. territories and other places that fall within a broader U.S. imperial orbit.
And it is not just in the tension between “expansion” and “empire” that the definitional blurriness of “expansion” arises. “Expansion” most clearly and narrowly applies to the territorial growth of the United States, a process associated with the U.S. government’s extension of territorial claims through diplomatic negotiation, purchase, and war. In this sense, it tends to be associated with the fifty-year period between the Louisiana Purchase and the Gadsden Purchase (and often to be linked to the even more problematic idea of “manifest destiny” [4]). However, as historians of expansion and the West have repeatedly shown, asserting a claim is just one piece of how any place and the people living in it become part of the nation. That larger process, involving the establishment of state sovereignty, extension of laws, extraction of resources, economic integration, settlement, and subordination or removal of Indigenous and other people, is a much more complicated, contingent, and contested process, and one that has both preceded and followed assertions of territorial claims. The ambiguity and breadth of “expansion” can lead to a lack of precision about how these processes have been entangled and which dynamics a historian intends to invoke in using the term.