Complex sentence: After the 1803 Louisiana Purchase by the United States, encroaching colonial settlement persuaded the Shawnee to negotiate an 1825 treaty ceding their Missouri lands for reservation lands in Kansas.
Split into simpler sentences: After the 1803 Louisiana Purchase by the United States. Encroaching colonial settlement persuaded the Shawnee to negotiate an 1825 treaty, ceding their Missouri lands for reservation lands in Kansas.