The Illinois Country continues to be a region of North America rich in history, both during the colonial period and as a western frontier of a young United States. Mark Milton Chambers adds to that history with Gray Gold: Lead Mining and Its Impact on the Natural and Cultural Environment, 1700–1840. His fascinating study builds upon the innovative scholarship of a number of historians in recent years, such as John Reda's From Furs to Farms: The Transformation of the Mississippi Valley, 1762–1825, which examines the two principal states that emerged from the region: Missouri and Illinois. Arguably the most prolific scholar in the field is historian Carl Ekberg, author of French Roots in the Illinois Country: The Mississippi Frontier in Colonial Times. Chambers took a course from Ekberg and ultimately answered his call for more scholarship on the “country full of mines,” an area on the west side of the Mississippi River in present-day Missouri. Chambers offers a thorough history of mining practices and their environmental impact over the course of the eighteenth century and into the first half of the nineteenth century as they evolved from Native American to an amalgamation with French practices to those employed by Americans, who used the latest innovations from Europe.Chambers notes that Native Americans had mined and smelted lead for centuries before contact with Europeans. They primarily used lead to make decorative objects and glaze paint for their pottery. It is highly likely, according to Chambers, that Mississippians learned of lead's uses by Puebloans of the Southwest, thereby establishing lead production in the Mississippi River Valley. A most interesting feature of Chambers's book is his examination of a mining middle ground that brought together Native Americans and Europeans at the turn of the eighteenth century. Kaskaskians and Tamaroas of the Illini Confederation worked with French settlers to establish a mining industry that used both Indigenous techniques as well as European practices. The French learned how to find lead deposits in the region with the help of their Indigenous guides and relied heavily upon them for the production of lead. The use of lead in the colonial era was extensive. Musket balls for firearms and baling seals for the fur trade were just two lead products that were in high demand. In addition, settlers, in the cash poor region, used the metal as currency for trade items and in the payment of wages. The French brought African slaves to the Illinois Country and began to use them in the production of lead. Even though lead mining and smelting were done on a small scale in comparison to later time periods, the environmental hazards of the process were already emerging.Even though French administration of the Mississippi River Valley came to an end in 1763, on the west side of the river, Spanish administration facilitated the expansion of lead mining and smelting. The Bourbon Reforms of the late colonial era allowed for the spread of new techniques in lead mining that included stone furnaces and shaft mining. The reforms also encouraged American and British miners to settle in the region. The result was a reinvigoration of the mining industry, although the amalgamated mining practices of the American Indians and the French continued. The Ste. Genevieve district, established by the Spanish, further solidified this portion of the Illinois Country as a center of mining. A number of business associations formed to create mines and mining communities. At this point, slaves became essential workers in the industry. Moses Austin, an American entrepreneur with extensive mining knowledge, arrived with his slaves from Virginia and became extremely influential in the industry, paving the way for American control of the region following the Louisiana Purchase. American manufacturers became interested in domestic lead production, which would relieve them of their dependence on British suppliers. Glass manufacturers, in particular, wanted a domestic source of zane, a lead product used in the production of glass bottles.After Americans took control of the region, Moses Austin wrote the first extensive mineralogical assessment for a national audience. Manufacturers soon began to produce lead products in the region itself along with continuing to export it to the industrializing northeast. The region became more populous, though concerns were mounting over the environmental consequences of lead mining on the landscape and on the bodies of both slaves and wage workers. Settlers became alarmed about the water supply for their villages and the effects lead poisoning had on their animals. These concerns only increased after Missouri statehood. The industry was taking on a modern form at this point, for mining and smelting were becoming less of a seasonal endeavor and more of a year-round system of production and employment. The emerging science of the era was employed to great effect, leading to greater efficiency and productivity. Nevertheless, lead poisoning and how to deal with it, posed a series of problems for the industry. While doctors and scientists grew concerned about the health effects of lead mining, business interests sought to downplay medical and environmental concerns.Chambers, over the course of his study, uses an impressive variety of primary sources. French, Spanish, and American journals, diaries, letters, scientific and government reports, and many other sources from the period bring to life a dynamic frontier that had extensive connections among empires, Native Americans, colonial regions, and the young United States. Gray Gold adds a useful analysis of an understudied element of mining history, expanding our understanding of mining in North America and placing Native Americans at the inception of the industry. Scholars and students interested in colonial history, the American frontier, mining, and environmental history will find Chambers's work of great value.