These data describe the percent of cropland harvested as wheat, corn, and soybean within each basin (basins 1-8, see accompanying shapefiles). Data are available for other crops; however, these three were chosen because wheat is a traditional crop that has been grown for a long time in the Basin and corn and soybeans have increased in recent times because of wetter conditions, the demand for biofuels, and advances in breeding short-season, drought-tolerant crops. The data come from the National Agricultural Statistics Service (NASS) Census of Agriculture (COA) and have estimates for 1974, 1978, 1982, 1986, 1992, 1997, 2002, 2007, and 2012. Years with missing data were estimated estimated using multivariate imputation of missing values with principal components analysis (PCA) via the function imputePCA in the R (R Core Team, 2015) package missMDA (Husson and Josse, 2015). In the interest of dimension reduction, the scores of the first principal component of principal component analysis, by basin, of the wheat, corn, and soy variables is included. Husson, F., and Josse, J., 2015, missMDA—Handling missing values with multivariate data analysis: R package version 1.9, https://CRAN.R-project.org/package=missMDA. R Core Team, 2015, R: A language and environment for statistical computing: R Foundation for Statistical Computing, Vienna, http://www.R-project.org.