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In 1989, the Board of Agriculture of the National Research Council (NRC) convened a committee to study how several Federal agencies (NRCS, BLM and USFS) inventory, classify and monitor rangelands (National Research Council, 1994). The committee stated that a standard method and a common data base for evaluating rangelands was needed. Traditional site classification methods based on potential or climax vegetation were difficult to use because of the inherent problems in the basic theories themselves. The classification problem was compounded by the lack of adequate inventory and monitoring methods to provide compatible data sets for multi-scale comparisons. According to the National Research Council, current rangeland inventories simply did not provide the data needed to support national assessments of rangeland health. We specifically addressed three of the five needs recognized by the NRC (1994) for a national system of inventorying and monitoring rangeland health: The collection of data by the same or similar methods that will enable data to be combined on a national level; The collection of data based on statistically valid sampling methods that allow evaluation of data at the site, state, regional and national levels; and The need for repeated sampling to monitor trends.