It is no coincidence that Missouri's official State Mineral is Galena, the major source of lead ore. For most of the late 19th and early 20th centuries, Missouri was the global leader in lead production, and even today some of the largest and most important remaining lead deposits in the world are located in southeast Missouri. Lead production has played an important role in the economic growth and development of Missouri. Estimates of the aggregate lead production in Missouri since mining began in the early 18th century, top 17 million tons, at a value of nearly $5 billion.