As the importance and dependence of specific mineral commodities increase, so does concern about their supply. The United States is currently 100 percent reliant on foreign sources for 20 mineral commodities and imports the majority of its supply of more than 50 mineral commodities. Mineral commodities that have important uses and face potential supply disruption are critical to American economic and national security. However, a mineral commodity's importance and the nature of its supply chain can change with time; a mineral commodity that may not have been considered critical 25 years ago may be critical today, and one considered critical today may not be so in the future. The U.S. Geological Survey has produced this volume to describe a select group of mineral commodities currently critical to our economy and security. For each mineral commodity covered, the authors provide a comprehensive look at (1) the commodity's use; (2) the geology and global distribution of the mineral deposit types that account for the present and possible future supply of the commodity; (3) the current status of production, reserves, and resources in the United States and globally; and (4) environmental considerations related to the commodity's production from different types of mineral deposits. The volume describes U.S. critical mineral resources in a global context, for no country can be self-sufficient for all its mineral commodity needs, and the United States will always rely on global mineral commodity supply chains. This volume provides the scientific understanding of critical mineral resources required for informed decisionmaking by those responsible for ensuring that the United States has a secure and sustainable supply of mineral commodities.

Nestled between the Rocky Mountains to the west and the High Plains to the east, Denver, Colorado, is nicknamed the Mile High City because its official elevation is exactly one mile above sea level. Over the past ten years, it has also been one of the country's fastest-growing metropolitan areas. In Denver's early days, its geographic proximity to the mineral-rich mountains attracted miners, and gold and silver booms and busts played a large role in its economic success. Today, its central location—between the west and east coasts and between major cities of the Midwest—makes it a key node for the distribution of goods and services as well as an optimal site for federal agencies and telecommunications companies. In Metropolitan Denver, Andrew R. Goetz and E. Eric Boschmann show how the city evolved from its origins as a mining town into a cosmopolitan metropolis. They chart the foundations of Denver's recent economic development—from mining and agriculture to energy, defense, and technology—and examine the challenges engendered by a postwar population explosion that led to increasing income inequality and rapid growth in the number of Latino residents. Highlighting the risks and rewards of regional collaboration in municipal governance, Goetz and Boschmann recount public works projects such as the construction of the Denver International Airport and explore the smart growth movement that shifted development from postwar low-density, automobile-based, suburban and exurban sprawl to higher-density, mixed use, transit-oriented urban centers. Because of its proximity to the mountains and generally sunny weather, Denver has a reputation as a very active, outdoor-oriented city and a desirable place to live and work. Metropolitan Denver reveals the purposeful civic decisions made regarding tourism, downtown urban revitalization, and cultural-led economic development that make the city a destination.