sentences:  Two mines operated primarily for their silver were the Bay Horse mine in Baker County, which produced 125,000 ounces (3.9 metric tons) of silver, and the Oregon King mine in Jefferson County, which produced 300,000 ounces (9.3 metric tons) of silver.The Pequea silver mine near Conestoga in Lancaster County was worked from before the Revolutionary War to 1875.A minor amount of mining was done about 1900.