American citizenship has evolved over time as immigration and assimilation policies have changed. Early controversies emerged over citizenship for free blacks before the Civil War and Native Americans. As immigration increased in the late 19th century, restrictions on immigration began due to nativist sentiment. Modern issues include debates over legal and illegal immigration. Assimilation approaches like the melting pot and multiculturalism reflect competing ideas about retaining or abandoning cultural traditions. Citizenship involves both rights and responsibilities of participation in civic life.