This large hand-drawn map shows a “rough sketch of the mining claims of Mariposa de Oro,” located in the Famatina Mountains on the eastern edge of the Andes in La Rioja Province, northwest Argentina.

The map primarily shows the claims belonging to William A Treloar, a British mining engineer whose name appears on the map several times. There is also a note in the upper right rwhich reads, “the numbered claims belong to W.A.T” Records show Treloar had been mining in the Rioja province since the mid-1870s. He seems to have made the much of his fortune by acquiring large mining areas, exploiting them, and then leasing out smaller portions to other claimants (who often did not fare particularly well). In 1892, Treloar took over the Mariposa claim from a French outfit, leased out portions to smaller operations, and sold off the whole thing a few years later. He also built a large estate in the nearby town of Chilecito, which was later left to his close friend Joaquin Gonzalez, a prominent writer, educator, and politician, who in turn bequeathed it to the University of La Plata.