The Tucson Ring is the most well known iron meteorite in the world primarily because of its exotic shape but also because of its storied history. It was first reported by Jose Velasco of Sonora, Mexico in 1845 from his treatise on mining in the region. He described a mountain pass, Puerta de los Muchacos (today known as Box Canyon), in the Sierra de la Madera range (Santa Rita Mountains today) where large masses of pure iron were found at the base of the mountains. He described how one of the medium-sized masses was taken to Tucson, 30 hard miles away, where it was used as an anvil for the garrison blacksmith. Somehow a second large mass was taken to the garrison between 1845 and 1850 again to be used as an anvil, and this meteorite became known as "The Carleton". Pieces of the Ring were analyzed in 1852 and determined to be of meteoritic origin. In 1856, The Ring was abandoned as an anvil until 1860 when medical officer Bernard Irwin found the abandoned Ring and took possession of it for the Smithsonian Institution. The Carleton went west to California for display until 1939 when it was purchased by the Smithsonian and reunited with the Ring in Washington.

The Tucson Ring is unusual in that its mineralogy indicates that it was formed during a cataclysmic event whereby a small planet or asteroid was blasted apart by gravitational shear or impact with another body. As the body broke apart, the molten material ejected into space cooled and formed meteoroids and new asteroids. The Tucson Ring cooled very quickly, indicating that it was part of a smaller remnant mass from the core or mantle of the destroyed planetoid. This is proven by the fact that the nickel-iron did not have time to crystallize and form the distinctive Widmanstatten figures that characterize and identify most iron meteorites the Tucson Ring will not show Widmanstatten figures when etched because it was quenched quickly after the cataclysm. The Ring also has inclusions of clear glasses, further proving that it was quickly cooled. The Tucson Ring is the most highly sought-after iron meteorite in the world because only a small piece was removed from a knob on the inside margin of the Ring for analysis by the Smithsonian and no more will ever be removed. This means that the supply of this meteorite amounts to only a few hundred grams available to all of the scientific institutions and collectors worldwide.