Complex sentence: Louis Auguste Benoist (1803--1867) was a pioneer banker and financier born August 13,1803, in St. Louis, Missouri, then a French settlement under Spanish rule and soon to become a possession of the United States under the Louisiana Purchase.
Split into simpler sentences: Louis Auguste Benoist (1803--1867) was a pioneer banker and financier. Born August 13,1803, in St. Louis, Missouri, then a French settlement under Spanish rule and soon to become a possession of the United States under the Louisiana Purchase.