The mines that were founded in the last half of the 19th century brought an international spotlight to Southern Arizona. Silver, placer gold, and the rich mineral wealth first drew adventurous prospectors, but soon came the settlers and major investors who built the mines that fed the world demand for copper. Arizona mines became unique test beds for new technology after the turn of the 20th century, as mining companies sought more economical and productive ways to extract precious metals. Some mining towns in Southern Arizona came and went, leaving no trail other than historic photographs. A few left scattered dilapidated buildings that remain today as ghost towns. Others grew into communities with stable populations and amenities like opera houses and theaters that joined the stores and saloons as they prospered.