McCarroll was born and raised in the Adirondacks. She attended a medical college in Chicago. She moved to Southern California in 1904 with her first husband, John Robertson. They had hoped that the desert climate would help him with his tuberculosis, but Robertson died in 1914. She later married Frank McCarroll, the local station manager for the Southern Pacific Railroad. From 1907 to 1916, she was the only physician regularly practicing in the vast desert between the Salton Sea and Palm Springs. She was also the only physician serving the area's five Indian reservations for the Bureau of Indian Affairs.