4 Forgotten National MonumentsU.S. National Monuments are natural and man-made sights that have been preserved and protected for their cultural, historical and scientific relevance. The title can be granted to anything from a coral reef to a civil war fortress and prehistoric pueblo. Mount Rushmore and the Statue of Liberty are among the more commonly known of the 129 national monuments spread throughout the United States and its territories. But there are plenty that are often overlooked or have fallen by the wayside.Castle Pinckney National Monument, South CarolinaCredit: Paul Briden/ShutterstockSet on Shute Folly Island in Charleston Harbor,...