Technical Abstract: The Grazing Lands component of the USDA-NRCS Conservation Effects Assessment Project (CEAP) is a national assessment of the environmental effects of management practices used on pasture and rangelands. The pasture subcomponent is based around applying ecological principles to temperate humid grazing lands. One of the first steps necessary is to develop a quantitative, ecologically-based classification system for pastures that parallels the Ecological Site Description system used in rangelands. This system must incorporate climate, soils, and topography, and be a suitable basis for studying potential community distributions and management effects. Development of such a system is difficult for the eastern United States: unlike in rangelands, referring to potential (forested) vegetation type is not relevant. Multivariate spatial analysis methods have been used to divide the northeastern United States into physical site types, and those have been correlated with land cover information to determine the characteristics of sites used for pasture, and to identify regional variation in such characteristics. Extensive field sampling data has been used to incorporate species information into this classification. This site classification is being used as a basis for creating state and transition models for grazed temperate grasslands, and for developing predictions of potential agricultural implications of climate change.