The papers of Maurice Rosenblatt (1915-2005) span the years 1910-2003, with the bulk of the material dating from 1942 to 2000. They relate primarily to his life as a lobbyist and focus on his work with the National Committee for an Effective Congress (NCEC). A large portion of the collection consists of material assembled by the NCEC to curb the power and influence of Senator Joseph McCarthy of Wisconsin in his opposition to communism. These efforts culminated in McCarthy's censure in the United States Senate in 1954. The Rosenblatt Papers consist of two parts.

Part I

Part I of the Rosenblatt Papers contains most of the material relating to his professional activities. It is organized in two series: the National Committee for an Effective Congress and Miscellany .

The National Committee for an Effective Congress files were compiled while Maurice Rosenblatt was the Washington director of the political interest group. A nonpartisan organization, NCEC was founded to raise funds and support the campaigns of liberal and internationalist candidates for the United States Congress. The NCEC series is arranged in three subseries: an Administrative File , McCarthy Clearing House files, and a Projects and Subjects file. The Administrative File contains correspondence, interoffice communications mostly between Rosenblatt and executive director George E. Agree, files documenting meetings, events, and fund-raising activities, newsletters and reports issued by the organization, and press coverage. The Projects and Subjects file documents political elections and the financial support given to congressional candidates and includes papers relating to the involvement of Rosenblatt and the NCEC in the establishment of the Democratic Study Group and the Foreign Policy Clearing House.

In 1953 Rosenblatt and the NCEC helped form the McCarthy Clearing House to oppose Senator Joseph McCarthy and his tactics. A main goal of the group was to make information about McCarthy available to the press, senators, and others working against him. This effort was funded by the NCEC. Participants included William Benton, Kenneth Birkhead, John Howe, Robert Nathan, and Gerhard P. Van Arkel. Contained in the McCarthy Clearing House files are notes and research material collected by Jack Anderson and Ronald W. May for their book McCarthy: The Man, the Senator, the “Ism” (1952), files created by Benton's attorney in support of Benton's lawsuit against Joseph McCarthy, items gathered by columnist Drew Pearson's attorney as part of Pearson's lawsuit against McCarthy, and material collected by Lucille Lang Olshine, a researcher employed by the clearing house. In 1954 the group spearheaded the efforts of Senator Ralph E. Flanders of Vermont who put forth a resolution in the Senate calling for Senator McCarthy's censure. Files on the clearing house's activities document the goals, strategy, and actions of this committee, and information on the censure resolution is extensive. Included in material related to Flanders are numerous letters sent to the senator in 1954 in response to his criticism of McCarthy. Most of the letters oppose Flanders's actions and express support for McCarthy and his methods of fighting communism.

In addition to material documenting actions of those opposing Joseph McCarthy, the McCarthy Clearing House subseries also contains subject files providing information relating to McCarthy's efforts, “McCarthyism,” and events of the period. Because material was originally filed using different methods when it was gathered from various sources and then intermingled through use by researchers before coming to the Library of Congress, items relating to any one topic may be found in more than one place in the collection. For example, a separate subject file on McCarthy compiled for McCarthy v. Benton is filed under William Benton's name and contains additional material on topics listed elsewhere.

The Miscellany series relates to Rosenblatt's life, activities, and interests outside of the National Committee for an Effective Congress. Files of the National Counsel Associates, a lobbying and consulting firm Rosenblatt established in the 1950s, principally relate to projects from the late 1980s and early 1990s. Included in a personal file is material relating to Rosenblatt's work as publicity director for the Draft Stevenson movement in the 1960 presidential campaign and to his work prior to the establishment of NCEC with organizations such as the Coordinating Committee for Democratic Action in New York and the American League for a Free Palestine, for which he lobbied Congress to gain American support for the establishment of a Jewish state in Palestine. Other material relating to the American Committee for a Free Palestine and the establishment of Israel located in the resource material for Rosenblatt's memoirs includes recollections from Peter Bergson and Harry Louis Selden with regard to their activities in the 1940s. Although Rosenblatt worked on his memoirs for over twenty years, he never completed the project. Other writings by Rosenblatt are included in a miscellaneous writings file. Material he wrote for NCEC is filed in that series.

Part II

Part II of the Rosenblatt Papers is organized in five series: Family Papers , Personal Correspondence , National Committee for an Effective Congress , Miscellany , and Frank Rosenblatt Papers .

The Family Papers contain correspondence between Maurice Rosenblatt and members of his family, especially his mother, Katherine, his sister, Bernice, and his younger brother, Frank. Most of the correspondence dates from Maurice's student days at the University of Wisconsin and his military service in World War II. Rosenblatt's letters from late 1944 and 1945 provide details about his time in New Guinea during the war.

The Personal Correspondence contains letters from Rosenblatt's friends and associates, mostly from the World War II period. Many letters were written by girlfriends from the home front. The series also contains a few letters written by Rosenblatt, including some he wrote to Laura Barone, to whom he was married for a short period in the 1950s.

The National Committee for an Effective Congress series complements the series of the same name in Part I. Included are additional letters from the public to Senator Flanders of Vermont in response to his criticism of Joseph McCarthy in 1954.

The Miscellany contains memorabilia, photographs, subject files, and writings. The photographs date from the 1940s until the early 1980s and depict Rosenblatt's military service, travel, and social gatherings. Included are photographs of Henry Steele Commager and Eugene J. McCarthy and pictures of a visit in 1977 with the writer Robert Graves (1895-1985). Subject files reflect some of Rosenblatt's activities prior to the founding of the National Committee for an Effective Congress, such as his association with the Coordinating Committee for Democratic Action and his work relating to Palestine, including as a member of the editorial board of The Answer: An American Weekly Dedicated to the Struggle for Hebrew National Liberation and the Independence of Palestine in 1947-1948. Writings in the Miscellany augment Rosenblatt's memoirs in Part I.

The Frank Rosenblatt Papers comprise the final series in Part II. Frank Rosenblatt (1928-1971), Maurice's younger brother, was an associate professor of neurobiology at Cornell University who invented the Perceptron, a type of artificial neural network. His papers include personal correspondence from the 1960s. Frank Rosenblatt's correspondence with his family, mostly from the 1940s, is part of the Family Papers series.