Complex sentence: In the mid- 1860s, Pratt met two aspiring young men, Charles Ellis and Henry H. Rogers in western Pennsylvania, and later purchased the entire future output of their small venture, Wamsutta Oil Refinery near Oil City, at a fixed price.
Split into simpler sentences: In the mid- 1860s, Pratt met two aspiring young men, Charles Ellis and Henry H. Rogers in western Pennsylvania. Pratt later purchased the entire future output of their small venture, Wamsutta Oil Refinery near Oil City, at a fixed price.