Complex sentence: In 1881, the West Chester and Philadelphia Railroad was consolidated into the P&BC, and the merged lines were controlled by the Philadelphia, Wilmington and Baltimore Railroad, which was itself controlled by the Pennsylvania Railroad (PRR).
Split into simpler sentences: In 1881, the West Chester and Philadelphia Railroad was consolidated into the P&BC, and the merged lines were controlled by the Philadelphia, Wilmington and Baltimore Railroad. All of these lines were controlled by the Pennsylvania Railroad (PRR).