Putnam was born to a prominent family from New England, his mother Louise Carleton Putnam, was the daughter of New Yorkpublishing magnate George W. Carleton. Paternally, he was a lineal descendant of American Revolutionary War general Israel Putnam. He was also related to the physical anthropologist Carleton Coon, with whom he corresponded closely regarding theories of anatomical and biological differences between human races. He was raised as part of the American Episcopal Church and remained a lifelong member. His best known book is entitled Race and Reason, an advocacy of racial segregation that originated in a letter he wrote to President Dwight Eisenhower protesting the end of segregation in U.S. public schools. According to Putnam, the immediate impetus for his letter to Eisenhower was the concurring opinion of Justice Frankfurter in Cooper v. Aaron, 358 U.S. 1, which Putnam refers to as "the recent Little Rock case". Elsewhere in the book Putnam critiques Brown v. Board of Education, 347 U.S. 483, calling for its reversal. Psychologist Henry Garrett wrote the introduction. In this book, Putnam wrote:
In the next 500,000,000,000 years I would be quite prepared to concede the possibility the Negro may, through normal processes of mutation and natural selection within his own race, eventually overtake and even surpass the white race. When the Negro has bred out his limitations over hundreds, or thousands, of years, it will be time enough to consider absorbing him in any such massive doses as would be involved in the South today.
The mulatto who was bent on making the nation mulatto was the real danger. His alliance with the white equalitarian often combined men who had nothing in common save a belief that they had a grudge against society. They regarded every Southerner who sensed the genetic truth as a bigot . Here were the men who needed to be reminded of the debt the Negro owed to white civilization.
Putnam also wrote a biographical book on Theodore Roosevelt's youth that was praised by Edmund Morris, the author of the best known biography of that president. Putnam admired Roosevelt's belief that "Teutonic English blood is the source of American greatness". Carleton Putnam died of pneumonia on Mar. 5, 1998. He was survived by his wife, Esther Mackenzie Willcox Auchincloss, a daughter, three grandchildren, a stepdaughter, and three step-grandchildren. He was previously married to Lucy Chapman Putnam.
