The Adirondack and St. Lawrence Railroad operated between DeKalb Junction and Hermon in St. Lawrence County, New York over a four-mile standard gauge railroad. The Adirondack & St. Lawrence was owned by the and incorporated on April 19, 1906, and shortly thereafter the line was opened. A parallel railroad of the , was abandoned in the early 1870s. Traffic was low and in 1925 the A.& St.L. line was abandoned and torn up. Still today the right-of-way can be observed near East DeKalb. In Hermon, the roadbed is now used by Water Street.