Mercer's artistic talent was recognized early and she earned a scholarship a 15 to enroll in the State Normal School in Livingston, Sumter County. Julia Tutwiler, president of the school, carried several of Mercer's sculptures to Birmingham in 1907 for an exhibit at the Alabama State Fairgrounds. The pieces were later displayed at the headquarters of the Commercial Club of Birmingham. They were seen there by Moretti, who invited the girl to move to his home studio in Sylacauga to become his apprentice. She accepted immediately and shared the Moretti household with Giuseppe and his wife, Dorothea.
In Moretti's studio, Mercer's role grew quickly. She prepared plaster models for the master's use while carving full-size marbles and inscribed Moretti's name on his finished works. She was also given the opportunity to pursue her own work, selling her first piece in 1911. She assisted in the completion of most of Moretti's large works, such as the Patrick O'Reilly statue and Mary Cahalan statues in Birmingham. She also created the Montgomery Museum of Fine Arts' Flimp Fountain, which she worked on from 1909 to 1936. Her best-known work is a bas-relief panel depicting the Pied Piper, of which numerous copies exist in the state. She also executed a memorial for her early supporter, Tutwiler, in 1933.
In 1911, Moretti was commissioned to create 125 sculptures for the exterior of the Centro Gallego Club in Havana, Cuba. He and Mercer moved to Havana while Dorothea remained in New York, where they had just moved the year before. The arrangement, and the fact that Mercer destroyed her letters from her time in Cuba, have led to speculation on the nature of her relationship with her master, but there is no indication that their affection for each other exceeded the limits of propriety.
Mercer continued to live with the Morettis during another stay in Sylacauga as well as in New York and in Pittsburgh, Pennsylvania. In 1924 they moved to Italy, first to Florence and then to a villa in San Remo. Moretti placed Mercer in charge of overseeing the construction of a cottage for her and Dorothea to share after his death, which came in 1935. Mercer designed his tombstone in green granite with her statue of an angel on top. She also continued to operate Moretti's studio professionally — completing works he had left and conducting business as usual.
The two women returned to the United State in 1939 in anticipation of World War II. They settled in Boston where Mercer sculpted and taught college art classes. After Mrs Moretti's death in 1958 she moved in with relatives in Florida. In 1964 she returned to her home county, renting half of a house in Demopolis where she spent the rest of her life creating mostly small paintings and trinkets and writing verse.
She also took charge of Moretti's legacy, donating many of his works to museums and libraries in Alabama and around the country. She compiled a Complete List of the Sculpture of Giuseppe Moretti: From the Time He Came to the United States in 1888 until His Death in 1935, which remains the definitive guide to Moretti's work. She was a vocal critic of the misuse of Vulcan to advertise products at the Fairgrounds and, later, of his use as a traffic safety beacon. She donated Moretti's scrapbooks to the Julia Tutwiler Library at the University of West Alabama in 1983.
Mercer's last home and the adjacent Laird Cottage in Demopolis have since been converted by Gwyn Turner into the Geneva Mercer Museum.
- Jordan, Phillip (March 24, 2005) "Moretti's assistant: Alabama's own Geneva Mercer." Birmingham Weekly.
- Geneva Mercer profile at the Alabama Women's Hall of Fame