 After Paradise Point Road, the highway follows a winding, southeasterly course along Tupper Lake, passing little more than dense forests while crossing over the Bog River near its mouth.NY 421 follows the lake to its southern tip, where the route ends at an intersection with NY 30 just west of the St. Lawrence–Franklin county line.In 1923, the New York State Legislature passed a law authorizing the construction of a highway connecting Route 24 (an unsigned legislative route that is now part of NY 30) to the new Veterans' Mountain Camp, an American Legion camp on Tupper Lake.