Complex sentence: Grinnell, Minturn & Co. was one of the leading transatlantic shipping companies in the middle 19th century, and is probably best known today as being the owner and operator of the "Flying Cloud", arguably the greatest of the clipper ships.
Split into simpler sentences: Grinnell, Minturn & Co. was one of the leading transatlantic shipping companies in the middle 19th century. It is probably best known today as being the owner and operator of the "Flying Cloud", arguably the greatest of the clipper ships.