Short answers, pulled from the story.
Citizenship and nationality are conceptually different dimensions of collective membership. International law does not usually use the term citizenship to refer to nationality. In most cases citizenship is a consequence of nationality, but the two are not synonymous.
Citizenship in ancient Greece is associated with the early city-states, or poleis, where it developed as a status for male free residents of the city. The Athenian politician Solon made reforms in the early Athenian state that one view holds made citizenship genuinely functional. Women, slaves, and resident foreigners known as metics were excluded.
In 1857 the US Supreme Court ruled in Dred Scott v. Sandford that a free negro of the African race, whose ancestors were brought to this country and sold as slaves, is not a citizen within the meaning of the Constitution. This decision was overturned by the 14th Amendment, ratified on the 9th of July 1868.
Native Americans were granted full US citizenship by the Indian Citizenship Act in 1924. However, some state laws still prevented them from voting well into the 1960s, and New Mexico became the last state to enfranchise Native Americans in 1962.
The Reich Citizenship Law of 1935 classified inhabitants into citizens, subjects, and aliens. Citizens were males of German or so-called Aryan heritage who had completed military service. Subjects were those born within German borders who did not meet racial criteria, including all women. Aliens were citizens of other states.
The Maastricht Treaty established that every person holding the nationality of an EU Member State is also a citizen of the Union. The amended EC Treaty granted a general right of non-discrimination under Article 12, a limited right to free movement and residence in other Member States under Article 18, and certain political rights under Articles 18-21 and 225.