Complex sentence: In the 1980's Donald Trump owned 57 acres of land just south of Riverside Park that had been the Penn Central freight rail yard (seldom used since the 1968 merger of the financially ailing New York Central and Pennsylvania Railroad).
Split into simpler sentences: In the 1980's Donald Trump owned 57 acres of land just south of Riverside Park. This land was originally part of the Penn Central freight rail yard (but seldom used since the 1968 merger of the financially ailing New York Central and Pennsylvania Railroad).