Chapter 1 introduces the basic patterns in mid-nineteenth-century Mexico’s energy regime. After a brief overview of Mexico’s longer history, it presents a panoramic view of Mexican society in the 1850s and analyzes the relationship between economic activity, environmental conditions, and the country’s energy regime, which depended on the annual solar cycle. It sketches the basic contours of Mexico’s pre–fossil fuel era, providing a baseline against which the social, economic, and environmental developments examined in subsequent chapters can be gauged.