The Great Salt Lake is the largest saltwater lake in the United States, and, in fact, in the Western Hemisphere. It is located within the state of Utah, near Salt Lake City. It used to be a lot bigger during the Pleistocene, covering nearly half of Utah. Since it's in the Great Basin, no water in it will flow to the Ocean; thus, the reason why it is so salty is due to eroded minerals building up over hundreds of thousands of years.
American sculptor Robert Smithson constructed a large jetty into the Great Salt Lake as a work of art. The varying mineral and algae content of the water produces a gradient of color along the jetty.