Complex sentence: Mathias Bruen, who bought the property at a sheriff's sale in 1817, transformed himself into one of the wealthiest men in America while he lived here, and his descendants made large contributions to America's social and political history.
Split into simpler sentences: Mathias Bruen, who bought the property at a sheriff's sale in 1817, became one of the wealthiest men in America while he lived here. His descendants made large contributions to America's social and political history.