Civil War Union Brevet Brigadier General. As a volunteer in the Mexican War, he was sent to the southwest. At the conclusion of the war, he was drawn to the gold fields of northern California. As the Civil War began to unfold, he was increasingly concerned about the status of the state of California. During the summer of 1864, Emperor Napoleon III of France tried to set up Maxmilian I as Emperor of Mexico. The move was perceived as a threat to the security of the American southwest in the midst of the Civil War. In response, the Seventh California Volunteer Infantry was created. The regiment included many veterans of the Mexican War. Because many of the volunteers were from the gold fields of northern California, they were referred to as the "Gold Diggers." Lewis was made their commanding colonel. After training at the Presidio of San Francisco, they were assigned to southern Arizona where they were to guard against potential incursions by the Mexican Empire and its French allies. They were also to operate against the Apaches in the area. The site of Fort Mason near Calabazas was selected by Colonel Lewis. The somewhat swampy location of the fort on the banks of the Santa Cruz River produced such dire conditions that the unit acquired a new nickname - the "Hungry Seventh." In late 1865, Lewis gave refuge to the governor of Sonoran province, Ignacio Pesqueira, who was fleeing from the forces of Maximilian. During the Civil War, the Seventh California managed to put small expeditions in the field to show the flag and demonstrate that southern Arizona and California would remain a part of the United States. After the threat of French and Mexican intervention was removed in March of 1866, the Seventh was ordered back to the Presidio in San Francisco. They were mustered out of service in May of that year. For his services in raising, organizing, and training the Seventh California Infantry, Lewis were breveted a brigadier general on March 13, 1865. After he was mustered out of service, he went back to Arizona and established a ranch near Tubac. He served one term in the Arizona territorial legislature before moving to San Diego, California where he briefly became involved in publishing and politics before his death.