The American Rapids begin at the upstream end of Goat Island and drop about 50 feet in elevation to the brink of the American Falls and Bridal Veil Falls. Though only a few feet deep, the swift rapids are extremely dangerous because the hard dolostone riverbed has been worn smooth by water but is also fractured and covered with numerous potholes. In the 1750's, Daniel Chabert de Joncaire built a sawmill and dug a small canal along these rapids, creating an island later called Willow Island, and during the French and Indian War he burned the sawmill to keep it out of British hands. In 1805, Augustus and Peter Porter and other local businessmen purchased land near the falls, and the rebuilt sawmill, along with other industries, helped establish the village that would eventually become Niagara Falls. During construction of the Robert Moses Parkway in the 1960s, Joncaire's canal was filled in. In the spring of 1969, a cofferdam of boulders, gravel, and soil was built from the mainland to the upper end of Goat Island to stop water from flowing over the American Falls and Bridal Veil Falls, and between June and November scientists and engineers conducted a geologic study that concluded the talus below the falls should not be removed and that Niagara Falls should continue retreating upstream through its natural process. The lower section of the American Rapids has been illuminated at night since 1989, and the upper section since 1998.