The National Lakes Assessment (NLA) is a first-ever statistically-valid survey of the biological condition of lakes and reservoirs throughout the U.S. The U.S. Environmental Protection Agency (EPA) worked with states and tribes to conduct the assessment in 2007. Data for each parameter sampled in the National Lakes Assessment (NLA) are available for downloading in a series of files as comma separated values (.csv). Each .csv data file has a companion text file (.txt) that lists a dataset label and individual descriptions for each variable. Users should view the .txt files first to help guide their understanding and use of the data.