Alaska is frequently imagined by the Lower 48 as the Last Frontier, a vast pristine wilderness, and an essential component to United States energy independence. Alaska is also warming at twice the rate of the rest of the United States and is a contested site for oil and gas development in the Arctic. With over 222 million acres of land controlled by federal government—Alaska represents a third of all federal land holdings, reflecting the legacies of settler colonialism, the conservation movement, and resource extraction while raising questions about the future of decarbonization and decolonization amidst the climate crisis and Indigenous-led movements for sovereignty, climate justice, and land (Byrd 2011; Waziyatawin 2012; Estes 2019; Dhillon 2022). Through anthropological ethnography in Alaska and multidisciplinary research, this dissertation brings together climate, energy, and settler colonial studies to examine how the U.S. settler colonial project as a process of internal expansion enacted through reiterative and theoretical frontiers formed settler identities, notions of democracy and populism, and understandings of nature vis- à-vis resource abundance and extraction and the wilderness that impact the broader fights over public lands—which should also be understood as unceded Indigenous lands—decolonization, climate change, and energy transition.