Complex sentence: One early needle dam maintains the level of Lake Lucerne in Lucerne, Switzerland by restricting the flow of the Reuss River, several are still in operation on the Meuse River, France and others were built in the United States in the 19th century.
Split into simpler sentences: One early needle dam maintains the level of Lake Lucerne in Lucerne, Switzerland by restricting the flow of the Reuss River. Other needle dams were built in the United States in the 19th century.