American Immigration: A Very Short Introduction traces three massive waves of immigration from the mid-nineteenth century to the present, and analyzes the nature of immigration as a purposeful, structured activity, attitudes supporting or hostile to immigration, policies and laws regulating immigration, and the nature of and prospects for assimilation. There have been some dramatic developments since 2011, including the crisis along the southwestern border and the intense conflict over illegal immigration. The population of the United States has diverse sources: territorial acquisition through conquest and colonialism, the slave trade, and voluntary immigration. Many Americans value the memory of immigrant ancestors, and are sentimentally inclined to immigrant strivings. Alongside this sits the perception that immigration destabilizes social order, cultural coherence, job markets, and political alignments. The nearly 250 years of American nationhood has been characterized by both support for openness to immigration and embrace of a cosmopolitan formulation of American identity and for restrictions and assertions of belief in a core Anglo-American national character.