African Americans (also referred to as Black Americans or Afro-Americans) are an ethnic group of Americans with total or partial ancestry from any of the black racial groups of Africa. The phrase generally refers to descendants of enslaved black people who are from the United States. African Americans constitute the third largest ethnic group and the second largest racial group in the US, after White Americans and Hispanic and Latino Americans. Most African Americans are descendants of enslaved peoples within the boundaries of the present United States. On average, African Americans are of West/Central African and European descent, and some also have Native American ancestry. According to U.S. Census Bureau data, African immigrants generally do not self-identify as African American. The overwhelming majority of African immigrants identify instead with their own respective ethnicities (≈95%). Immigrants from some Caribbean, Central American, and South American nations and their descendants may or may not also self-identify with the term. African-American history starts in the 16th century, with peoples from West Africa forcibly taken as slaves to Latin America, and in the 17th century with West African slaves taken to English colonies in North America. After the founding of the United States, black people continued to be enslaved, and the last four million black slaves were only liberated after the Civil War in 1865. Due to notions of white supremacy, they were treated as second-class citizens. The Naturalization Act of 1790 limited U.S. citizenship to whites only, and only white men who owned property could vote. These circumstances were changed by Reconstruction, development of the black community, participation in the great military conflicts of the United States, the elimination of racial segregation, and the civil rights movement which sought political and social freedom. In 2008, Barack Obama became the first African American to be elected President of the United States.