In 1909, Leopold was assigned to the Forest Service's District 3 in the Arizona and New Mexico territories. At first, he was a forest assistant at the Apache National Forest in the Arizona Territory. In 1911, he was transferred to the Carson National Forest in northern New Mexico. Leopold's career, which kept him in New Mexico until 1924, included developing the first comprehensive management plan for the Grand Canyon, writing the Forest Service's first game and fish handbook, and proposing Gila Wilderness Area, the first national wilderness area in the Forest Service system.