In the early 1900s, the Phelps-Dodge Copper Company sought to connect their New Cornelia Copper Mine in Ajo (pronounced "AY-ho") with smelters in Tuscon, AZ. Since Tucson was located on Southern Pacific's Sunset Route, Phelps-Dodge decided to build a railroad line north out of Ajo to the nearest point on the Sunset Route at Gila Bend, some 30 miles away. Thus, on May 10, 1915, Phelps-Dodge incorporated their own railroad company, the Tucson, Cornelia and Gila Bend Railroad, to construct a 43-mile line between the copper mine at Ajo and a connection with the Southern Pacific at Gila Bend; the line was completed and opened to freight and passenger traffic on February 20, 1916.
The line saw considerable business, both freight- and passenger-wise for most of its life. However, as copper production at the New Cornelia mine declined in the 1970s and into the 80s, the railroad ceased being profitable, and the line was closed on April 12, 1985, bringing to an end over 71 years of service.
The TC&GB is one of only a few railroads in the United States that has sustained continuous passenger operations for over 70 years.
Both the freight and passenger depots of the TC&GB in Ajo still exist; the passenger station has been renovated into a local business.
The line was re-opened temporarily in 1995-1998 so the smelter in Ajo could be dismantled and removed; the tracks have remained dormant ever since.