Circular 39 - Wetlands of the United States

The Wetlands of the United States was published in 1959 by the U.S. Fish and Wildlife Service and is commonly referred to as "Circular 39." The Circular 39 Classification System was the first method that the U.S. Fish and Wildlife Service used to classify wetland basins in the U.S. It is composed of 20 wetland types of which eight are found in Minnesota.

The Circular 39 classification was inconsistently applied among regions primarily because of a lack of detail in the definitions of wetland types. In 1975 the U.S. Fish and Wildlife Service developed a new classification that would serve as the basis of the new National Wetlands Inventory.

Minnesota Wetland Types
The eight wetland types found in Minnesota are:

Type 1: Seasonally Flooded Basin, Floodplain Forest

Type 2: Wet Meadow, Fresh Wet Meadow, Wet To Wet-Mesic Prairie, Sedge Meadow, And Calcareous Fen

Type 3: Shallow Marsh

Type 4: Deep Marsh

Type 5: Shallow Open Water

Type 6: Shrub Swamp; Shrub Carr, Alder Thicket

Type 7: Wooded Swamps; Hardwood Swamp, Coniferous Swamp

Type 8: Bogs; Coniferous Bogs, Open Bogs
A detailed description of each wetland type can be viewed on the Minnesota Wetland Types page.