Okamanpeedan Lake, partially located in Martin County, Minnesota, and Emmet County, Iowa, is also known as Tuttle Lake. Okamanpeedan Lake is a roughly 2,300-acre (9.3 km²) riverine lake located on the East Fork of the Des Moines River. It has an average depth of about four to six feet (1.2 to 1.8 m). The lake has a contributing watershed of approximately 120,056 acres (486 km²).The lake is situated in a glacial till plain and is generally in an area dominated by loamy, poorly drained soils. The area is primarily level but does have some rolling hills.
Okamanpeedan Lake was explored by Joseph Nicollet during his 1838 expedition. He recognized the native American name for the lake, which means "nesting place of the herons", because of the large number of herons nesting in tall trees along its shores. Calvin Tuttle was the first settler along the lake, thus that became another name for this body of water.