Marginalization refers to the social process by which certain groups are pushed to the edges of society, limiting their access to resources, rights, and opportunities. This often leads to a lack of representation and voice in political, economic, and cultural spheres. In the context of American interest in New Mexico following the Mexican-American War, this concept is significant as it highlights how various populations, particularly Native Americans and Mexicans, experienced disenfranchisement and exclusion as the U.S. expanded its influence in the region.