Gilbert Cranberg was born in New York City on February 20, 1925. After serving in World War II he graduated magna cum laude and Phi Beta Kappa with a BA in journalism and political science from Syracuse University in 1949. During the summers while he was attending Syracuse, he travelled abroad, attending the University of Norway at Oslo and the University of Debrecen in Hungary. In 1956 he received a degree in Social Science from Drake University.

He joined the editorial page staff of the Des Moines Register in 1950, at the age of 24. He stayed until 1982, serving as editor of the editorial pages during his last seven years. It was his only newspaper job. During that time, The Des Moines Register published the Register as a morning paper and the Tribune as an afternoon paper; the papers ran different editorial pages, though the staff was the same. Cranberg was interested in fairness and he served on the board of the ACLU. Michael Gartner, the editor of the Register, said in an editorial about hiring Cranberg's successor that she or he must be characterized by " . . . a passionate belief in human rights, a strong bias toward free trade, a commitment to human dignity, a compassion for the poor person and the poor nation, a dislike for the tyrant and demagogue, a distrust of secrecy and a distaste for special privilege" and continued that Cranberg had been the perfect editor in demonstrating and practicing those traits. Cranberg's particular interests were in legal and journalistic questions, corrections, civil rights, and social welfare. Through his editorials he was responsible for establishing one of the nation's first bail reform programs. He received awards from numerous social organizations, such as the Iowa Council on Crime and Delinquency, the American Bar Association, and the Iowa Civil Liberties Association. He served as Chairman of the Professional Standards Committee of the National Conference of Editorial Writers on the executive board of that organization. He was a member of the Freedom of Information Committee of the American Society of Newspaper Editors and on that organization's Ethics Committee.

He wrote articles for The Christian Science Monitor, where he was a correspondent, Journalism Quarterly, Saturday Review, Columbia Journalism Review, The Nation, New Republic, Bulletin of the American Society of Newspaper Editors, New York Times, Washington Post, Los Angeles Times, USA TODAY, American Journalism Review, Nieman Reports, American Bar Association Journal, and Iowa Law Review. He lectured at Drake University and the University of Iowa. After he retired from the Des Moines Register in 1982, he joined the faculty of the University of Iowa, where he taught until 2000, when he retired a second time.

He published several books, including Taking Stock: Journalism and the Publicly Traded Newspaper Company, 2001; The Business of News in the Publicly Traded Newspaper Company: Report of the Iowa Newspaper Research, 2000; and was co-author with Randall Bezanson and John Soloski of Libel Law and the Press: Myth and Reality, 1987.

Married in 1951, he and his wife Norma had four children.