The importance of rangeland monitoring and assessment (hereafter RMA) generally is accepted. This is evidenced by the emphasis on robust monitoring programs at national (e.g., the Natural Resources Conservation Service Natural Resources Inventory), regional (e.g., range-wide monitoring of sage grouse habitat), and local (e.g., allotment-level monitoring within the Bureau of Land Management and US Forest Service) levels despite tightening budgets. However, the importance and benefi ts of RMA based on ecological site potential is less well understood. The modern concept of an ecological site describes the potential vegetation communities that could occur on a site (states and phases) and the natural and human-caused processes that produce shifts from one phase to another and transitions between states.1 This concept evolved from that of the “range site,” which described a unique climax plant community that would occur in an area in the absence of disturbance (i.e., Clementsian succession). The range concept was broadened to include multiple successional pathways and to describe the ecological and management processes that lead to changes both within and among plant community states (i.e., different successional pathways) and different plant community phases (i.e., communities within states).2 An ecological site provides a standard reference for land management, research, and monitoring. The ecological site description informs managers as to what kinds of changes can be expected in response to management or disturbance and provides a reference for the interpretation of RMA data. It also informs managers about ecological potential in terms of vegetation composition and vegetation-dependent uses (e.g., grazing, wildlife habitat). In other words, the ecological site determines what is possible, the current state determines what is realistic, and the phase within a state conveys the current conditions and likelihood of future transitions. The concept of ecological sites and their current implementation via ecological site descriptions and associated geographic information system (GIS) spatial data layers provides a scalable framework for RMA. In addition, there are many practical uses of ecological sites for designing RMA programs and collecting and analyzing data from them. In this paper we describe an RMA framework based on ecological sites and present examples for several current and potential applications.