Thirteen major data sources for the study of American politics are examined with regard to their conceptual orientation, error structure, and inferential utility. A great deal of ephemera and measurement without theory is discovered. Few of the documents contain any serious discussion of error structure, although some do report “standard errors” based on naive sampling models. In addition to suggestions for improving the compilation of political statistics, recommendations for a basic minimum library of data sources for American politics are made: The Almanac of American Politics and the Statistical Abstract of the United States, followed by the Guide to U.S. Elections.