Since 1950, the United States Geological Survey (USGS) has collected and released data on national water use every five years for each state, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands. In November 2014, the USGS released water-use estimates for 2010. These data are collected from a variety of sources, including from national data sets, state agencies, questionnaires, and local contacts (Maupin et al. 2014). They include estimates of withdrawals of freshwater and saline water from groundwater and surface-water sources and water use by sector. Using these data and historic data from several other sources, this paper reviews national water-use trends, going as far back as 1900 in some cases. For this analysis, we use the term "water use" to refer to the amount of water withdrawn from the ground or diverted from a surface-water source for use. Our analysis finds that we have made considerable progress in managing the nation's water, with total water use less than it was in 1970, despite continued population and economic growth. Indeed, every sector, from agriculture to thermoelectric power generation, shows reductions in water use. National water use, however, remains high, and many freshwater systems are under stress from overuse. Moreover, climate change will exacerbate existing water resource challenges, affecting the supply, demand, and quality of the nation's water resources. In order to address these challenges, we must continue and even expand efforts to improve water-use efficiency in our homes, businesses, industries, and on our nation's farms.