Born in New York City in 1883, Gladwin worked in the city as a stockbroker from 1908 to 1922, his first successful career. However, in 1922 he decided to move west to California, and there he began work at the Santa Barbara Museum of Natural History, taking a special interest in the mutations of butterflies.
Gladwin's life took an interesting turn when he moved from a career as a stockbroker in New York City to working at the Santa Barbara Museum of Natural History, focusing on butterfly mutations.