The document outlines the history of US immigration through five eras: Open-Door (1789-1880), Door-Ajar (1880-1920), Pet-Door (1920-1965), Revolving-Door (1965-2001), and Storm-Door (2001-present). It discusses the major legislation and court cases that defined each era, as well as current issues around assimilation, economics, bilingualism, multiculturalism, and national security.