Complex sentence: When the Illinois Central Railroad was built, stopping in Tonica, Illinois, six miles away from Mount Palatine, rapid decline in enrollment ensued at Judson, and, became unprofitable, was sold in 1860 to the Catholic community in the vicinity.
Split into simpler sentences: When the Illinois Central Railroad was built, stopping in Tonica, Illinois, six miles away from Mount Palatine, rapid decline in enrollment ensued at Judson. This institution subsequently became unprofitable and was sold in 1860 to the Catholic community in the vicinity.