Ten thousand years ago, when glacial ice sheets melted, they left deposits of clay, gravel, and rock dust in the depressions formed in the plains by glacier movement. America's few walled glacial blue lakes were formed by nature. Iowa has two of three such lakes in the world, North Twin and West Okoboji. The third glacial blue lake is Lake Como, located in Switzerland, on the border nearest Italy.

Experts believe that North and South Twin were at one time one lake, 5 times as large as the present lakes. Season by season, as the waters froze and thawed more soil and rocks were pushed to the edges, gradually building a shore wall.

North Twin is clay and sand bottom and covers 569 acres. The lake is owned by the State of Iowa and is 2.9 miles long with shoreline of approximately 7 miles. There are approximately 325 private homes on the lakes.

Fishing
North Twin is regularly stocked with fish by the State Conservation Commission with walleye pike, northern pike, catfish, bass and tiger muskie. Through natural reproduction there are bullheads, crappies, perch, and yellow bass. Along North Twin's shores are three state parks and two county parks, all with fine sandy beaches. Thirty-five percent of the shoreline (over two miles) is available for public use.

Parks
The largest State Park on the East shoreline covers 15.5 acres with a shelter house, playground, and sanitary facilities. The other state parks, also with playground equipment, are on the west and north shores. Two county parks are both at the north end of the lake - Featherstone, covering 21 acres, with 3,000 feet of shoreline, and the boat access park on the northeast shore. Commercial and tent camping as well as cabin rental is available at Featherstone Park.

Multi-Purpose Trail
The seven-mile Twin Lakes trail encircle beautiful North Twin Lake, a jewel of Calhoun County. The trail may be used for bicycles and walking/jogging.

Boating
Several boat ramp accesses make boating the lake convenient. One is located at the south end of the lake; another is just south of the the outlet between the lakes, lower east side; and at the north end located in the Featherstone County Park.

South Twin Lake
The South Lake, sister to North Twin, covers 600 acres, and is owned by the State of Iowa. A shallow lake, it is a wildlife refuge, and is popular with migrating birds as a regularly used migration stop. The Twin Lakes Golf Club is located on the east side.

Electricity, natural gas, public water service, cable TV, and sanitary sewer service serve the lake area.