The Savanna Army Depot Activity was located in southwestern Jo Daviess and northwestern Carroll counties, Illinois. Founded in 1917, it was used for munitions manufacturing, testing and storage. The 13,062-acre area contains about 7,000 acres of uplands and 5,500 acres of bottomlands. The entire area is listed as a statewide significant natural area by the Illinois Natural Areas Inventory. At least 47 Illinois endangered and threatened plant and animal species have been observed at the Depot.

In 1995, the Depot was placed on the Army's base closure list and was officially closed on March 18, 2000. The land is being divided between Federal and State agencies and the Local Redevelopment Authority (LRA). The U.S. Fish and Wildlife Service (FWS) will receive 9,857 acres to become the Lost Mound Unit of the Upper Mississippi River National Wildlife and Fish Refuge. The unit derives its name from a prominent geologic feature ‘Lost Mound’ located in the adjacent bluffland. The Illinois Department of Natural Resources (IDNR) will receive 270 acres (Primm’s Pond and Beaty Creek areas). The Lost Mound Unit will be managed by the FWS in cooperation with the IDNR. The LRA plans to redevelop 2,932 acres.

Significance of Lost Mound for Conservation

Before Europeans settled the Midwest in the 1800's, Illinois was covered with 22 million acres of prairie. Since then, the Prairie State has lost all but about 2,300 acres of its original high quality prairie. Most of these remnants are small and not large enough to provide adequate habitat for grassland animals that have declined or disappeared along with the prairie.

In 2004, Lost Mound was designated as one of 48 Important Bird Areas throughout Illinois by the National Audubon Society. The uplands at Lost Mound support the largest contiguous remnant of sand prairie/sand savanna in Illinois, making it a vital refuge for plants, animals, and people. Because of this large expanse of habitat, the prairie provides significant habitat for declining grassland birds, including upland sandpiper, loggerhead shrike, western meadowlark, and grasshopper, Henslow’s, and lark sparrows. In addition, Lost Mound and the adjacent bluffland is the only location in Illinois where a continuum of riverine, prairie, and upland forest communities occur as an ecosystem landscape. The diversity of habitats is important for both breeding and migrant birds. The 235 bird species recorded at Lost Mound include 103 spring or fall migrants, 37 year-round residents, 83 summer residents, and 12 winter residents. Lost Mound is home for both nesting and large concentrations of wintering bald eagles.

Topography and Soils

The topography of the uplands is generally one of level to rolling plains of sand deposited by glacial melt waters and blown into widespread areas east of the river. In many areas, the sand has migrated onto the bluffs and uplands east of the river terraces. In places, dunes 20 to 40 feet high have been formed and blowouts are common in unstabilized sand. The upland soils are derived from sand and sandy material. Other soils occur in depressions surrounded by sand. The soils are generally droughty and subject to wind erosion. Low areas are generally wet. The bottomlands of the upper Mississippi River are characterized by broad floodplains and gravel terraces formed by glacial flood waters. Bottomland soils are from recent alluvium and glacial outwash. They are poorly drained, alkaline to slightly acidic, and vary from sandy to clayey.

Plants and Animals of the Uplands

The uplands at Lost Mound support an extensive sand prairie, as well as smaller areas of sand savanna and forest. Various stages of natural vegetation succession are present, including dunes, blowouts, and flat sand prairie which are characteristic of this natural division. Little bluestem and June grass are common grass species in the uplands and black oak is the dominant sand savanna tree. At least 13 endangered or threatened plant species occur in the uplands, including species whose only known location in Illinois is at the Depot. In 1996, blue grama was found. This grass was considered extirpated from Illinois and the Lost Mound population was last observed in 1907; this is the only known location of this grass in Illinois.

At least 175 bird species have been observed in the uplands at Lost Mound. The large expanse of sand prairie/sand savanna contains perhaps the largest populations in Illinois of sensitive species such as the grasshopper sparrow and western meadowlark. In addition to those already mentioned are the blue grosbeak, field sparrow, dickcissel, vesper sparrow, eastern meadowlark, bobolink, orchard oriole, and red-headed woodpecker. A number of characteristic sand prairie reptiles are found at Lost Mound, including the ornate box turtle and western hognose snake. Resident mammals include deer, rabbit, badger, and western harvest mouse.

Plants and Animals of the Bottomlands

The bottomlands of Lost Mound are a mosaic of floodplain forest and Mississippi River backwater sloughs, lakes, and islands. The Floodplain forest is composed of hardwood trees, predominately silver maple and cottonwood. Emergent marshes and wet meadows are dominated by herbaceous vegetation. Open water areas have floating and submerged aquatic vegetation. These areas are important feeding and nesting grounds for many animals, including wading birds and waterfowl, particularly wood ducks. At least 167 species of birds have been observed in the bottomlands at Lost Mound. Several rare or listed species utilize the bottomlands, including the bald eagle and Blanding’s turtle.

The Mississippi River channel and backwater sloughs and lakes at Lost Mound support excellent fisheries and provide habitat for at least 75 species of fish. Common fish species include walleye, sauger, channel catfish, crappie, and largemouth bass. Also found here are the endangered lake sturgeon, western sand darter, and pallid shiner. Several rare species of mussels such as the Higgens eye pearly mussel have been found at Lost Mound. A mussel sanctuary is located north of Lock and Dam 12 to help protect this unique part of our natural heritage.

Mississippi River Sand Areas and Bottomlands

The upland portion of Lost Mound lies within the Mississippi River Section of the Illinois River and Mississippi River Sand Areas Natural Division. This natural division encompasses the sand areas and dunes in the bottomlands of the Illinois and Mississippi rivers and includes the "perched dunes" atop the bluffs near Hanover. Scrub oak forest and dry sand prairie are the natural vegetation of this division. Several plant species found here are more typical of the short-grass prairies to the west of Illinois. Several "relict" western amphibians and reptiles are known only from these sand areas. The adjacent blufflands lie within the Wisconsin Driftless Natural Division.

The bottomlands of Lost Mound are within the Mississippi River Portion of the Upper Mississippi River and Illinois River Bottomlands Division. Much of this area was originally forested, but prairie and marsh also occurred.

Text by Ed Anderson, Illinois Department of Natural Resources (updated Feb 25, 2005)