Hopatcong is a borough in southern Sussex County along the western and southern shores of Lake Hopatcong, New Jersey's largest lake. The community developed from a collection of seasonal resort neighborhoods into a year-round residential municipality. Local roads follow the lake's irregular shoreline and wooded hills, connecting distinct neighborhoods, marinas, parks, restaurants, schools, and civic facilities. Routes 181 and 183 provide access toward Mount Arlington, Roxbury, Stanhope, and Interstate 80. Lake recreation remains central to the borough's identity, with boating, fishing, swimming, and waterfront activity increasing during warmer months. Residential areas range from older cottages near the water to later homes on wooded slopes and inland streets. Hopatcong borders several Morris and Sussex County communities, reflecting the lake's role as a regional destination. Its shoreline geography, recreation-based history, and dispersed neighborhood pattern distinguish it from the denser towns along the Interstate 80 corridor.