Complex sentence: The Main Line of Public Works was completed in 1834 and was sold to the Pennsylvania Railroad on June 25,1857 for $7,500,000 which within a year had replaced the Philadelphia-Pittsburgh route with an entirely rail based system.
Split into simpler sentences: The Main Line of Public Works was completed in 1834 and was sold to the Pennsylvania Railroad on June 25,1857, for $7,500,000. Within a year, the PRR replaced the Philadelphia-Pittsburgh route with an entirely rail-based system.