Who was Charles Eastman?

Who was Charles Eastman?  Be sure to include attitudes in both American Indian and white cultures toward Eastman.  What do you think of Eastman (back it up with sources)?

http://www.usdakotawar.org/history/ohiyesa-charles-eastman

http://brianaltonenmph.com/6-medical-anthropology/charles-eastman/charles-eastman-ohiyesa-brief-biography/

http://college.cengage.com/english/lauter/heath/4e/students/author_pages/late_nineteenth/eastmansioux_ch.html