The Wiretapping and Surveillance subseries (1.26 linear feet) contains materials on the use of wiretapping and surveillance techniques on individuals by the police, government agencies, and private employers. The files contain correspondence, printed materials, court documents, legislation, and memoranda. Consult the Police Practices subseries under the Due Process heading for collateral information.

The Civil Rights subseries (11.76 linear feet) contains legal, administrative, and correspondence files relating to the ACLU's involvement in the protection of individual liberties. The subseries is organized chronologically with various headings for each year (though not all headings appear in every year) and contains newspaper clippings, correspondence, memoranda, and background papers. While the bulk of materials deals with the rights of African-Americans, several files contain material related to the liberties of Jews, Mexican-Americans, aliens, and the disabled.

Correspondence, court documents, newspaper clippings, and reports related to elections and voting rights comprise the materials in this subseries (2.1 linear feet). Such issues as the required number of signatures for a new party to be recognized; the rights of minority parties (such as the Progressive Party, Socialist Party or Christian Nationalist Party) to partake in the election process; discussions of the laws concerning United States citizens and foreign elections; and election laws in general are detailed. One topic covered in great detail is reapportionment: there are many discussions of legislation related to the Supreme Court's ruling ( Baker v. Carr) requiring state legislatures to apportion their representation on the basis of population.

The International Civil Liberties subseries (19 linear feet) contains press releases, correspondence with officials like General Douglas MacArthur, and reports on censorship, labor laws and U.S. policy. Much of this material attests to Roger Baldwin's personal interest in international civil liberties during this period.

This subseries consists of a variety of material gathered together by the ACLU as "miscellaneous" and of material placed under that heading by the processors of this project. It includes correspondence, memoranda, manuscripts, press releases, clippings, articles, legal documents, and bail bonds and is arranged chronologically. It includes materials on presidential elections from 1948 to 1964 and on election and campaign reform including statements and testimony by members of the ACLU and also questionnaires of candidate's views on civil liberties issues; information on municipal and state ordinances as well as a book of cancelled bail bonds from 1927-1931, showing the grassroots legal efforts of the ACLU to defend the rights of those associated with unpopular organizations; yearly compilations of "Descriptive Summaries of ACLU Case Actions Taken in Defense of Civil Liberties" (1946-1953); "Reference Books" compiled by the staff of the ACLU (1921-1946) containing memoranda of law and summary reports related to various civil liberties issues; information on films and television programs about civil liberties, such as "Inherit the Wind" and a television program on Sacco and Vanzetti; and manuscripts relating to civil liberties topics written by staffers of the ACLU and also by those outside the organization and submitted to the ACLU for approval or editorial comment. There are also a few files containing correspondence from the 1940s and 1950s which was at that time considered "confidential" and a "Survey of Communist-Oriented Organizations and Publications" compiled at the request of Roger Baldwin in 1946.