The conflict between the US government and the Mormons in Utah Territory during the second half of the nineteenth century reflected shifts in the American territorial system. Through a repudiation of religious practices and dismantling of the Latter-Day Saints' Church as an institution, the federal government demonstrated a willingness and ability to interfere with and regulate traditional local issues such as marriage and religion. This provided a foundation for the changes to the territorial system outlined by the Supreme Court in the Insular Cases. Scholars have overlooked the continuities between earlier territorial policy and the post-Insular Cases colonial system. Linking the struggle over authority in Utah Territory with the outcome of the Insular Cases as a component of territorial policy history fills this gap and helps to illuminate the policy connections between continental expansion and overseas expansion.