The first 500 acres of CCESR were acquired in the early 1940s with the understanding that they would be kept in their natural condition and used for scientific and educational purposes. Funds for acquisition of additional land, development of permanent buildings and preparation of accurate maps became available from a variety of sources including personal contributions, the National Science Foundation, the Max Fleischmann Foundation, the Minnesota Natural Resources Commission and the US Land and Water Conservation Program. Cedar Creek lies at the boundary between prairie and forest. It is a mosaic of uplands dominated by oak savanna, prairie, hardwood forest, pine forests, and abandoned agricultural fields and of lowlands comprised of ash and cedar swamps, acid bogs, marshes, and sedge meadows. Large tracts of the pre-agricultural ecosystems of the region are preserved within its boundaries as is a successional chronosequence of more than 80 old fields of known history. A program of prescribed burns, begun in 1964 in a large tract of native oak savanna, has 12 blocks with fire frequencies ranging from one per year, to one per 7 years, to unburned controls. These have diverged dramatically in their vegetation and soils in response to fire frequency and some areas are now exhibiting characteristics not seen in this region since settlement in the 1800s. The soils of Cedar Creek, derived from a glacial outwash sandplain, span five of the ten soil orders. Upland soils are nitrogen poor: numerous nutrient addition experiments performed in both old fields and native savanna have shown that nitrogen is the major soil resource that limits plant growth. Cedar Creek has a continental climate with cold winters, hot summers, and precipitation (66 cm/yr) spread fairly evenly throughout the year. The mean July temperature is 22.2OC while the mean January temperature is -lOoC.