What is the only U.S. state with a Spanish motto?

Like other state mottoes, Montana's Spanish Oro y Plata was conceived as the Montanans were deciding on an official seal for the new Montana Territory. In 1865, shortly after Montana had gained territorial status, a committee, chaired by Mr. Francis R. Thompson, got together to determine an appropriate design for the new seal. The committee agreed that the seal should incorporate certain essential elements of Montana's economy and its future.

As the committee discussed the new seal the question of a territorial motto was introduced. Based on the mineral wealth that Montana had produced since 1862, members favored "Gold and Silver" as a meaningful motto for Montana Territory. Someone thought the motto would have a nice ring in Spanish and, again, there was agreement. Seal design and motto were presented to the Legislature on February 4, 1865. At this time there was a suggestion that "El Dorado," meaning "the place of gold," might be more appropriate than simply "Gold and Silver." But both houses approved the seal with the motto Oro y Plata and Territorial Governor Sidney Edgerton signed the bill into law on February 9, 1865.

The seal has been modified, to some degree, over the years, but the motto has remained: Oro y Plata.