Newton Falls is a hamlet of 400 located within Town of Clifton in Saint Lawrence County, New York in the United States. The hamlet is located within the Adirondack Park. The area is known in part for its ZIP code, which is 13666. The hamlet was named for James Newton, who built a sawmill in 1894 which became the Newton Falls Paper Mill; it closed in 2000. It was reopened in 2007 as Newton Falls Fine Paper through the efforts of former mill workers and town residents.