Carmer was born in Cortland, New York. His father, Willis Griswold Carmer, was the principal of Dansville High School. His mother, Mary Lamson Carmer, grew up on a farm in Dryden, New York.
When he was five his father became principal of Albion High School in Albion, New York, which is upstate from New York City in the western part of the state. He graduated from Albion High School in 1910 and entered his father's alma mater, Hamilton College, where he earned his undergraduate degree. He subsequently received a master's degree from Harvard.
He taught briefly at Syracuse University before accepting a position at the University of Alabama in 1927. After six years in Alabama, he returned to New York and married artist Elizabeth Black. He also became an assistant editor at Vanity Fair. In his later years, Carmer would work as a folklore consultant for Walt Disney Productions and produce a folklore radio series called "Your Neck o' the Woods." He also produced four albums of regional songs. He died on September 11, 1976, in Bronxville, New York.
When Carmer arrived in Tuscaloosa, Alabama, one of his new colleagues warned him, "...if I knew you well enough to advise you, I'd say, 'For God's sake, get out of here before it's too late.'" This reference was evidently about the state of Alabama's racial relations at the time. Carmer, however, stayed at the University for six years, taking notes and writing what would become his most famous book, Stars Fell on Alabama.
In the book, Carmer recounted the time he spent traveling throughout the state. He wrote about the people, places, and events he witnessed, such as a Ku Klux Klan rally and interactions with ordinary Alabama men and women.
One example of the book's prose was this description of a Sacred Harp singing:
The church was full now. People stood along the walls and the doorway was packed. Crowds were huddled outside each window singing lustily...there were surely more than two thousand people...Hard blows of sound beat upon the walls and rafters with inexorable regularity. All in a moment the constant beat took hold. There was a swift crescendo. Muscles were tensing, eyes brightening.
Carmer also wrote about the myths, legends, and local superstitions of what he called "Conjure Country" (which was his nickname for southeast Alabama). He credited folklorist Ruby Pickens Tartt with providing some of the folklore and songs for this book, and he based the character Mary Louise on her.
First published in 1934, Stars Fell on Alabama hit the bestseller lists and established Carmer's reputation. Literary critic R. L. Duffus of The New York Times praised the book and said Carmer had a gift for "extracting from what he sees, hears and feels an essence which is fundamentally poetic." The book has been subsequently republished a number of times, most recently in 2000 with a new introduction by Howell Raines.
The title of the book referred to a spectacular occurrence of the Leonid meteor shower that was observed in Alabama on November 12–13, 1833. As reported by the Florence Gazette: "[There were] thousands of luminous bodies shooting across the firmament in every direction. There was little wind and not a trace of clouds, and the meteors succeeded each other in quick succession."
Sections of Carmer's book were adapted by Brad Vice in his short story "The Bear Bryant Funeral Train." His failure to acknowledge his debt to Carmer led the organizers of the Flannery O'Connor Award for Short Fiction to revoke the prize he was given in 2004.
After the success of Stars Fell on Alabama, Carmer returned to the upstate New York region he had grown up in. He documented the myths and stories of the region, including the Cardiff Giant hoax, and wrote a new book, Listen for a Lonesome Drum. He followed this up with a sequel in 1949, Dark Trees to the Wind.
In 1939 Carmer wrote a well-received volume in the Rivers of America Series, The Hudson River. In 1942 he became the Editor for the Rivers of America Series, edited The Songs of the Rivers of America (1942) and wrote The Susquehanna (1955). In all, Carmer wrote 37 books. He was considered one of America's most popular writers during the 1940s and 1950s.