Chapter 4 shows how state power and industrial interests turned oil into Mexico’s most important energy source in the first half of the twentieth century. In the 1890s, Mexico imported US crude and refined it domestically to be used as a source of artificial illumination and industrial lubricant. Reliance on imported oil ended when domestic production on a commercial scale began after 1901. By 1921, Mexico was the second largest oil producer in the world after the USA, representing one-quarter of total global output that year. By the 1930s, Mexico’s electricity generation, industries, and transportation (railroads and motor vehicles) largely relied on oil. By mid-century, the majority of energy consumed in Mexico was derived from oil and increasing amounts of natural gas (typically mixed with oil in underground deposits).