"US senator from the 1800s" includes Hiram R. Revels, who served in office 1870 - 1871 — the Reconstruction Era. He was elected by the Mississippi State legislature on a vote of 81 to 15 to finish a term left vacant. He also was of Native American ancestry. After his brief term was over he became President of Alcorn Agricultural and Mechanical College.

https://en.wikipedia.org/wiki/Hiram_R._Revels