The U.S. State Department Central Files are the definitive source of American diplomatic reporting on political, military, social, and economic developments throughout the world in the 20th century. Concentrating exclusively on those Central Files that have not been microfilmed by the National Archives or other publishers, UPA's microfilm editions of the Central Files nonetheless dwarf the State Department's very selective volumes of the Foreign Relations of the United States (FRUS). Containing less than one percent of the material in the Central Files, FRUS focuses on U.S. relations with individual countries but does not include coverage of many of the key topics to which the majority of the original files are devoted. Each part of the Central Files contains a wide range of materials from U.S. diplomats in foreign countries: special reports on political and military affairs; studies and statistics on socioeconomic matters; interviews and minutes of meetings with foreign government officials; court proceedings and other legal documents; full texts of important letters, instructions, and cables sent and received by U.S. diplomatic personnel; voluminous reports and translations from foreign journals and newspapers; and countless translations of high-level foreign government documents. The complete and unedited Confidential U.S. State Department Central Files for Mexico from 1940 through 1959 contain over a quarter of a million pages of American diplomatic reporting on both Mexican and inter-American affairs, providing historians, political scientists, and students with a wide range of research opportunities. During this dynamic period Mexico restructured its economy, accelerated the trend toward industrialization and urbanization, and inaugurated an unbroken line of civilian presidents in contrast to the military influence of the earlier 1900s. Coverage of these trends, electoral politics, labor issues, communism, financial affairs, and the relationship of church and state, make this set of primary materials essential for understanding an eventful period of political, economic, and social transformation in Mexico and Latin America.