This publication presents a national study of outdoor recreation trends as part of the 2010 Renewable Resources Planning Act Assessment by the Forest Service, U.S. Department of Agriculture. The objectives are to review past trends in outdoor recreation participation by Americans, to describe in detail current outdoor recreation participation patterns, and to compare patterns across regional and demographic strata. Further objectives include describing recreation activity participation on public and private lands and providing projections of outdoor recreation participation out to the year 2060. One overriding national trend is quite evident: the mix of outdoor activities chosen by Americans and the relative popularity of activities overall have been evolving over the last several decades. One general category of activity that has been showing growth in the first decade of the 21st century is nature-based recreation. Between 2000 and 2009, the number of people who participated in nature-based outdoor recreation grew by 7.1 percent and the number of activity days grew about 40 percent. Among types of nature-based recreation, motorized activities showed growth up to about 2005, but then ended up toward the end of the 2000-2009 decade at about the same level as in 2000. The trend in hunting, fishing, and backcountry activities remained relatively flat during this period. Various forms of skiing, including snowboarding, declined during this decade. The clear growth area was within the overall group of activities oriented toward viewing and photographing nature. Generally, outdoor recreation activities are projected to grow in number of participants out to 2060. Population growth is projected to be the primary driver of growth in number of adult participants under each Resources Planning Act Assessment scenario. The top five activities in terms of growth of number of participants are developed skiing, other skiing, challenge activities, equestrian activities, and motorized water activities. The lowest rates of participant growth are visiting primitive areas, motorized off-road activities, motorized snow activities, hunting, fishing, and floating water activities. At the same time, a number of activities are projected to decline in per-capita adult participation rates.