The Wilderness Act of 1964 established a National Wilderness Preservation System (NWPS) "to secure for the American people of present and future generations the benefits of an enduring resource of wilderness." The Act states that wilderness areas shall be administered "for the use and enjoyment of the American people in such manner as will leave them unimpaired for future use and enjoyment as wilderness." Moreover, it is the responsibility of each agency that administers wilderness to preserve each area's "wilderness character." Since 1964, more than 100 pieces of legislation have created an NWPS of over 100 million acres, in well over 600 individual wildernesses, administered by the U.S. Department of the Interior's Bureau of Land Management (BLM), Fish and Wildlife Service (FWS), and National Park Service (NPS); and the U.S. Department of Agriculture's Forest Service (FS). To provide for the use and enjoyment of these areas, while preserving their wilderness character, it is important for management agencies to monitor wilderness recreation visitors and the impacts they cause. Some people state that the Wilderness Act mandates that recreation impacts not be allowed to increase following wilderness designation (Worf 2001). Ideally, baseline conditions should be inventoried at the time each area is designated as wilderness and added to the NWPS, and then periodically monitored in the future to assess trends in conditions and the efficacy of existing recreation management programs. Such data will become increasingly valuable to future attempts to evaluate trends in the wilderness character of each area in the NWPS. Although baseline recreation conditions have been inventoried in many wildernesses, such data are lacking in many others. Moreover, the distribution of wildernesses with baseline recreation data is not equitable across the nation or the four agencies that manage wilderness. This report is an assessment of Wilderness Visitors and Recreation Impacts: Baseline Data Available for Twentieth Century Conditions David N. Cole Vita Wright the status of baseline recreation monitoring data for all wildernesses in the NWPS at the end of the twentieth century. It documents the proportion of the NWPS that has baseline data on recreation visitors and impacts, which wildernesses have this data, and where they are located. It identifies the types of data that have been collected, the types of sampling designs that have been employed, and how and where data have been stored. This compilation should help researchers identify wildernesses where trends can be assessed and help wilderness managers identify other managers who might be contacted about how to initiate and implement new studies. The data listed in this report are all we will ever have to gain perspective on the condition of designated wilderness in the twentieth century regarding recreation visitors and impacts. Because managers and the interested public, in future decades and centuries, will want to know what these places were like, these data will become increasingly valuable. Although some of the data are published in reports or have been carefully archived, most are stored on paper files in ranger offices, where they are vulnerable to loss. We strongly encourage agency personnel to recognize the future value of this data and invest in archiving it in such a manner that its perpetuation is ensured. These data could be the basis for valuable assessments of recreation and impact trends across the NWPS. This report begins with an overview of the status of recreation-related monitoring across the NWPS. Three types of studies are surveyed: those that provide (1) campsite impact data, (2) trail impact data, and (3) information about visitor characteristics.