Theodore Fagan was born in Buenos Aires, Argentina on February 21, 1921. He was of Jewish-English descent, and his early education included five years at a boarding school in England. He completed a Civil Engineering degree in Argentina in 1943, and two years later, moved to New York. Within months, Fagan was hired as a United Nations Spanish, French, and English interpreter. One of his early assignments was the Nuremberg War Trials (1946). Throughout his 30-year involvement with the UN, he interpreted speeches from leaders such as Prime Minister Fidel Castro and President Léopold Sédar Senghor of Senegal.

Fagan was also an indefatigable writer. His many writings include two historical novels (one on Eva Perón; one about the famous 19th Century Parisian lawsuit of La Roncière), the historical drama Elizabeth Rex, which was produced in Los Angeles in 1963, and his memoirs on his work with the UN. Fagan also had a lifelong passion for music and collected music memorabilia and recordings. After retiring from the UN at 55, he collaborated with William R. Moran on The Encyclopedic Discography of Victor Recordings. Matrix series 1 through 4999: the Victor Talking Machine Company, 24 April 1903 to 7 January 1908, which was published by Greenwood Press in 1986. Fagan died in New York in 1987.

The Fagan Collection consists primarily of reel to reel tapes (1033). The rest of the materials are music memorabilia, Fagan's writings, and documents concerning the UN.