Franklin Pierce Lake, also known as Jackman Reservoir, was formed in 1926 when Jackman Dam and Power Plant was built thereby flooding a section of the North Branch River.
The lake covers an area of approximately 519 acres of which about 1/3 is in Antrim and 2/3 is in Hillsborough. In rough measures it is about 2 miles long and a half mile wide. The mean depth is 4.6 meters while the maximum depth is 9.6 meters. A map is available at NH Fish and Game website.
It is considered to be a ‘warm water fishery’. The New Hampshire Fish and Game Department has determined that the lake contains Northern pike, smallmouth bass, largemouth bass, black crappie, yellow perch, white perch, bluegill, common sunfish, and brown bullhead (hornpout; catfish). The New Hampshire Fish and Game Department also stock it with a small number of rainbow trout and brown trout each year.
The Jackman Power Station is operated by PSNH and controls the water level of the lake at the dam. They generally lower the lake each fall starting gradually after Labor Day eventually lowering the level of the lake about 20 feet by January. They allow the spring melt off and spring rains to bring the water level back up to normal (about 770 feet above sea level) by Memorial Day.
Boating is allowed but as with all lakes, power boat operators must have a Safe Boater Certificate and they must keep their speed down to steerage speed whenever within 150’ feet of shore. Hillsborough’s Manahan Park is the only public boat ramp and beach on the lake.
Fortunately the lake has had no known infestation to date of the exotic invasive plants that have caused problems for many New Hampshire lakes but this is a continuing threat.