The Cheshire-Sullivan county line crosses the north section of Highland Lake (see map). This hotspot is in Cheshire County. Birders who carefully keep bird records by the county will want to be aware of the location of the county line and start a new checklist for birds seen in Sullivan County.

Highland Lake is 697 acres located in Sullivan and Cheshire counties in southwestern New Hampshire in the towns of Washington and Stoddard. The lake has two outlets. The north outlet feeds Shedd Brook, while the south outlet flows through Island Pond to the North Branch of the Contoocook River. The northern end of the lake is only accessible by boat through a channel approximately 50 feet wide.

The lake has been a popular site for recreational boating during the summer and snowmobiling during the winter since before the 1960s. Waterskiers are a frequent sight, and seaplanes are known to occasionally use the lake. Most of the lakeside real estate has seasonal and year-round residences. The Highland Lake Marina (the waterway's only such establishment) is located at the end of Shedd Hill Road. It is open during summer weekends and offers boat storage, docking, and recreational merchandise. There is also a diner attached.