Complex sentence: The Pittsburg and Shawmut Railroad is often confused with the Pittsburg, Shawmut and Northern Railroad from which the P&S had its origins, but the two were \xEF\xBB\xBF separate and unrelated companies after their 1916 split.
Split into simpler sentences: The Pittsburg and Shawmut Railroad is often confused with the similarly named Pittsburg, Shawmut and Northern Railroad from which the P&S had its origins. In fact the two were separate and unrelated companies after their 1916 split.