Complex sentence: Timber pirates continued to thrive in the Great Lakes for several years afterwards and at the same time there were pirates on the northern Mississippi River and the American navy launched another seperate operation against timber pirates in the Calcasieu River of Louisiana.
Split into simpler sentences: Timber pirates continued to thrive in the Great Lakes for several years afterwards. At the same time there were timber pirates on the northern Mississippi River and the American navy launched another seperate operation against timber pirates in the Calcasieu River of Louisiana.