Connecticut Lakes

First, Second, and Third Connecticut Lake (bottom to top), northern New Hampshire

The Connecticut Lakes are a group of lakes in Coos County, northern New Hampshire, United States, situated along the headwaters of the Connecticut River. They are accessed via the northernmost segment of U.S. Route 3, between the village of Pittsburg and the Canada port of entry south of Chartierville, Quebec. The lakes are located within the boundaries of Pittsburg, but are far from the town center. Connecticut Lakes State Forest adjoins them.

There are four lakes: First, Second, Third and Fourth Connecticut Lake, numerically running south to north. First Connecticut Lake is the largest. Fourth is the smallest, northernmost, and the source of the Connecticut River. The only access to this lake is via the Fourth Connecticut Lake Trail, which goes in and out of Canada. All lakes are north of the 45th parallel.

First Connecticut Lake

First Connecticut Lake
Location	Coos County, New Hampshire
Coordinates	45°5′37″N 71°14′52″W
Primary inflows	Connecticut River
Primary outflows	Connecticut River
Basin countries	United States
Max. length	5.3 mi (8.5 km)
Max. width	2.7 mi (4.3 km)
Surface area	3,071 acres (1,243 ha)
Average depth	56 ft (17 m)
Max. depth	163 ft (50 m)
Surface elevation	1,638 ft (499 m)
Settlements	Pittsburg

First Connecticut Lake is located in the town of Pittsburg, 5 miles (8 km) northeast of the village center. At 3,071 acres (1,243 ha), it is the eighth-largest lake located entirely in New Hampshire. It is the lowest (and largest) of the chain of lakes near the headwaters of the Connecticut River.

Fish species include landlocked salmon and lake trout.

Second Connecticut Lake

Second Connecticut Lake
Location	Coos County, New Hampshire
Coordinates	45°9′23″N 71°10′14″W
Primary inflows	Connecticut River
Primary outflows	Connecticut River
Basin countries	United States
Max. length	3.1 mi (5.0 km)
Max. width	1.3 mi (2.1 km)
Surface area	1,102 acres (4 km2)
Average depth	20 ft (6.1 m)
Max. depth	63 ft (19 m)
Surface elevation	1,866 ft (569 m)
Islands	3
Settlements	Pittsburg

Second Connecticut Lake, known in the past as Lake Carmel, is an 1,102-acre (4 km²) water body in the town of Pittsburg, situated 2 miles (3 km) upstream from First Connecticut Lake.

Fish species include brook trout, landlocked salmon, and lake trout.

Third Connecticut Lake

Third Connecticut Lake
Location	Coos County, New Hampshire
Coordinates	45°14′15″N 71°12′0″W
Primary inflows	Connecticut River
Primary outflows	Connecticut River
Basin countries	United States
Max. length	1.1 mi (1.8 km)
Max. width	0.5 mi (0.80 km)
Surface area	231 acres (93 ha)
Average depth	42 ft (13 m)
Max. depth	101 ft (31 m)
Surface elevation	2,188 ft (667 m)
Settlements	Pittsburg

Third Connecticut Lake, at one time known as Lake St. Sophia, is a 231-acre (93 ha) water body in the town of Pittsburg, situated 5 miles (8 km) upstream from Second Connecticut Lake and less than 1 mile (1.6 km) south of the Canada–United States border. The lake is the third in a chain of lakes marking the headwaters of the Connecticut River. It is approximately 100 feet (30 m) deep at its deepest part.

Fish species include rainbow trout and lake trout.

Fourth Connecticut Lake

Fourth Connecticut Lake
Location	Pittsburg, Coos County, New Hampshire
Coordinates	45°14′52″N 71°12′52″W
Primary outflows	Connecticut River
Basin countries	United States
Max. length	0.1 miles (.16 km)
Surface area	1.8 acres (0.73 ha)
Surface elevation	2,670 ft (810 m)
Settlements	Pittsburg

The Fourth Connecticut Lake is the northernmost, smallest and most remote of the Connecticut Lakes in New Hampshire. It is the source of the Connecticut River, situated 0.5 miles (0.80 km) upstream from and 482 feet (147 m) higher than Third Connecticut Lake. The Fourth Connecticut Lake Trail, which criss-crosses the international border between the United States and Canada, leads hikers to the lake. The land surrounding the lake is owned by The Nature Conservancy. The Fourth Lake is immediately to the northwest of the third lake.

Connecticut Lakes Natural Area

The 25,000 acres (10,000 ha) surrounding the lakes was set aside as a land conservation project in 2002 by the New Hampshire Fish and Game Department. The protected area is within the towns of Clarksville and Pittsburg, up to the border with Canada.