Pickerel Lake is a 955-acre spring-fed lake located in Day County, South Dakota, United States. Pickerel Lake is part of the Glacial Lakes Region that encompasses much of Northeast South Dakota and stretches along the Coteau des Prairies hills. The area was formed thousands of years ago by glacial activity. Many of the depressions left behind were filled by melting glaciers. This area is also referred to as the Prairie Pothole Region. Pickerel Lake is one of the deepest natural lakes in South Dakota. The name originated from an American Indian name meaning "where you spear long fish." Excursion boats were common until the early 1900s.