Fleming worked as a prospector and developer of Chloride Flats mining property, west of the town. There, a small community began, known as Camp Fleming. He later acquired much ranch property, amassing a large fortune. Fleming captained the local militia in the Geronimo and Victorio campaigns in 1882 and 1885. He was mayor of Silver City from 1885-1906. During the Spanish-American War, he was the chief recruiter of Rough Riders, but was unable to join the group because of the death of one of his children on the eve of their departure. Fleming was interested in higher education, and his efforts in Santa Fe led to the establishment of the New Mexico Territorial Normal School (1892) in Silver City.