Question: What tribe what American Horse a part of?
Answer: 
American Horse (Oglala Lakota: "Wašíčuŋ Tȟašúŋke" in Standard Lakota Orthography) (a/k/a "American Horse the Elder") (1830–September 9, 1876) was an Oglala Lakota warrior chief renowned for Spartan courage and honor.
American Horse (Oglala Lakota: "Wašíčuŋ Tȟašúŋke" in Standard Lakota Orthography) (a/k/a "American Horse the Elder") (1830–September 9, 1876) was an Oglala Lakota warrior chief renowned for Spartan courage and honor.