Complex sentence: Sarah DeRemer Knauss (née Clark; September 24,1880--December 30,1999) was an American supercentenarian who is the oldest person ever from the United States, as well as the second-oldest fully documented person ever behind Jeanne Calment.
Split into simpler sentences: Sarah DeRemer Knauss (née Clark; September 24,1880--December 30,1999) was an American supercentenarian. Knauss is the oldest person ever from the United States, as well as the second-oldest fully documented person ever behind Jeanne Calment.