Lake Byllesby lies in the Cannon River Valley located about 30 miles due south of downtown St. Paul along the south border of Dakota County and the northwest border of Goodhue County. The lake essentially is bisected throughout its length by the two adjacent counties. It sits between the municipalities of Cannon Falls near the east end and Randoph near the west end. The IBA is bounded by Hwy. 56 on the west, Co. Rd. 88 on the north, the eastern boundary of Lake Byllesby Regional Park on the east and the shore of the lake on the south. This boundary includes the lake and the county owned and managed Regional Park and adjacent lands on the north.

From St. Paul, take Hi 55 south to where it joins Hi 52. Take Hi 52 south to the Hampton exit. Follow CR 56 south to CR 88. The west end of Lake Byllesby is just southeast of this intersection.

Lake Byllesby is an impounded lake resulting from damming the Cannon River in 1910 just above the town of Cannon Falls (1). At approximately 580 ha (1,435 acres), it is the largest lake away from the Mississippi and Minnesota River corridors in each of the two counties and is also the largest "inland" lake in the ten contiguous counties comprising the southeast corner of Minnesota. The lake is shallow, averaging 11.6 ft. (1) throughout becoming most shallow at the far west end where the Cannon River enters the lake. At this location, extensive alluvial mudflats are exposed when lake levels are lowered. The lake is owned by the Minnesota Department of Natural Resources and is managed through a cooperative agreement with North American Hydro. The current management plan requires the lake level to be lowered each spring to minimize groundwater impacts on the planting of crops on adjacent farm lands. This level is maintained until May 15 at which time the level is allowed to rise to a summer pool level of 856.7 ft. above msl. In most years, this lowered level results in exposing extensive alluvial mudflats and adjacent shallow water areas that are preferred habitat for an impressive diversity of migratory bird species including shorebirds, ducks, geese, swans, herons, pelicans, gulls, and terns. Shorebirds annually are represented at Lake Byllesby in numbers and diversity of species not found elsewhere in eastern Minnesota.

Land ownership is a mix of private and public. The principal public landowner on the Dakota County side of the lake is Dakota County, Department of Parks and Recreation, and consists of Lake Byllesby Regional Park. The principal adjacent landowner on the Goodhue side of the lake is Goodhue County. The remainder of the adjacent land is in private ownership.