This narrow gauge, coal-burning steam locomotive pulled trains of copper ore at a mine in eastern Arizona.

It was built by the H. K. Porter Company in February 1896 for the Arizona Copper Company in Clifton, to haul ore from the mountaintop Coronado Mine to an incline which lowered the cars to the valley below. It was nicknamed "Rattlesnake" for the way it rattled along the twisting tracks.

When the mine closed in 1923, this engine was abandoned on the mountaintop. It was rescued in 1990 by the Phelps Dodge company, who donated it to the Museum of Discovery in Safford, Arizona. That museum became part of Arizona Eastern College in 2003, and the college donated it to this museum in 2019.

When the Coronado Mine was first built northwest of Morenci, ore was carried out by mule. The Coronado Incline was built in the 1880s so the ore could be transported in mining cars and lowered by cable to the valley below. Ore was sent over a one-mile aerial tramway to a point where it was loaded into cars for the remaining mile to the 1,200-foot incline.

Down below, the cars were taken to the processing facilities in Clifton. The entire Coronado Railroad from Clifton to Metcalf, including the inclines along the way, were built with a gauge between the rails of just 20 inches, referred to as "baby gauge." (Standard railroad gauge is 4 feet, 8 1/2 inches.) The Coronado Railroad was later widened to 36 inches.

Three "baby gauge" locomotives were built to pull the ore cars, two in 1887 and one in 1896. The latter was originally built with an 0-4-4T wheel arrangement, then the trailing truck was removed, and extra weight added in front for balance, making it an 0-4-0T. (The "T" indicates it is a "tank" engine, carrying its water in a saddle tank over the boiler instead of in a separate tender.) It burned coal which was carried in a bin in the cab.

In 1921, Phelps Dodge bought the Arizona Copper Company. They continued working the mine until 1923 when the incline and hoist equipment were shut down. There the engines sat, stranded, high on the hillside, stripped of "brass" during WWII, and inaccessible. On rare occasions, Phelps Dodge allowed access for hearty railfans to make the strenuous hike.

In the late 1980s, Phelps Dodge built a new drill road up the mountain as their mine expanded. This new access road enabled the three locomotives to be rescued. They were brought down the steep terrain on a loaded truck with a cable attached to a bulldozer.

After their recovery in March 1990, Phelps Dodge donated this one (No. 7) to the Museum of Discovery in Safford, Arizona. (No. 2 is currently on display at the former Arizona Mining & Mineral Museum in Phoenix; No. 5 is on display in Morenci, Arizona.)

When the Museum of Discovery′s restoration funding ran out, No. 7 was abandoned again, now in pieces. The museum became part of Arizona Eastern College′s Discovery Park Campus in 2003. Rediscovered there by the Arizona Railway Museum in 2019, there appeared to be enough pieces remaining (boiler, frame, wheels, cab, etc.) to make a decent cosmetic restoration and provide this historical Arizona gem a bright future.

The college obtained approval from Freeport McMoRan, which took over Phelps Dodge in 2007, to transfer ownership to the Arizona Railway Museum, and the acquisition began. The first few pieces arrived by truck at the museum′s Tumbleweed Park location on September 10, 2019, with the remainder following throughout 2020 and 2021, and work began on its restoration.

	11/14/2018 - The stripped boiler sitting in AEC Discovery Park.
	1990 - ACC No. 7 being rescued and given to the Museum of Discovery in Safford, AZ.
	For almost 70 years, these three locomotives sat, abandoned, waiting rescue.

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