Fourth Connecticut Lake is a foot-access-only preserve located at the U. S. /Canada border near Pittsburg, NH, accessible via a 1. 7-mile loop trail starting from the parking lot at the border crossing station on Route 3.

The trail is steep with granite sections that can be wet and slippery, requiring sturdy hiking shoes; no dogs, camping, hunting, or fishing are permitted.

This is the true headwaters of the Connecticut River—you can literally step across the small brook that marks the river's beginning at the southern end of the lake.