Water data play a crucial role in the development and assessment of sustainable water management strategies. Water resource assessments are needed for the planning, management, and the evaluation of current practices. They require environmental, climatic, hydrologic, hydrogeologic, industrial, agricultural, energy, and socioeconomic data to assess and accurately project the supply of and demand for water services. Given this context, we provide a review of the current state of publicly available water data in the United States. While considerable progress has been made in data science and model development in recent years, data limitations continue to hamper analytics. A brief overview of the water data sets available at the federal level is used to highlight the gaps in readily accessible water data in the United States. Then, we present a systematic review of 275 websites that provide water information collected at the state level. Data platforms are evaluated based on content (ground and surface water, water quality, and water use information) along with the analytical and exploratory tools that are offered. Wev discuss the degree to which existing state-level data sets could enrich the data available from federal sources and review some recent technological developments and initiatives that may modernize water data. We argue that a national water data portal, more comprehensive than the U.S. Energy Information Administration, addressing the significant gaps and centralizing water data is critical. It would serve to quantify the risks emerging from growing water stress and aging infrastructure and to better inform water management and investment decisions.