Sierra de la Plata (Spanish: Silver Mountains), was a legendary treasury of silver that was believed to be located in South America. The legend probably originated when the European survivors of a shipwreck were given abundant gifts of silver by the native peoples.
In the early 16th century, the estuary of the Uruguay and Paraná rivers was named by the Spaniards Río de la Plata (Silver River) because it was at first believed to be a river that led to the Sierra de la Plata. There is no evidence that any such mountain range of silver ever existed near the mouth of the Río de la Plata; to find them, one ought to travel to the far Andes, more than a thousand miles away. The closest mountain range that resembles the myth of the "Silver Mountains" is the range around Potosí in modern Bolivia, a town known for its rich silver veins.
From the rumor and the river, the modern country of Argentina also takes its name from the Latin word for silver, argentum.