Early humans encountered naturally seeping oil deposits at scattered sites throughout the world. Before the industrial era, the substance was used for illumination, medicinal purposes and, in a viscous form, caulking ships. Spanish explorers of California in the 1540s noticed oil; likewise, the later De Soto expedition found it in what is today Texas. Yale chemist Benjamin Silliman Jr. earned the title, "father of the petroleum industry," thanks to his development of fractionation methods essential for deriving distillates from oil. Experiments with “rock oil” by Silliman in 1855 revealed that highly useful kerosene and other byproducts could be produced economically. In 1859, “Colonel” Edwin L. Drake was hired to drill for oil, a novel idea at the time, at what became Titusville, Pennsylvania. “Drake’s Folly” eventually struck oil and began producing hundreds of barrels each month. The discovery touched off an oil rush nearly as intense as the earlier gold rush in California. Thousands of hopeful men poured into western Pennsylvania, hoping to strike it rich. Later discoveries were made in West Virginia and Ohio. Cleveland and Pittsburgh became leading refinement centers. Kerosene became widely available as a fuel for heating and illumination. Previously, the ability to illuminate one’s home was largely reserved for the wealthy who could tap dwindling supplies of whale oil; the poor were restricted to tallow candles that were notorious for their poor light and unpleasant odor. Discovery of cheap oil helped to change lifestyles throughout much of the world by enabling nighttime business and leisure activities. The oil era coincided with development of the steel industry. Lubricants were needed for the new machinery of the industrial age. Such business luminaries as John D. Rockefeller expressed an early interest in the oil business, but he was negatively impressed by the chaos of the Pennsylvania oil fields. He understood that oil could fulfill its potential only if its production were stringently centralized—and he capitalized on the situation. The Pennsylvania oil heydey did not last long, but huge new discoveries were made in Louisiana, Texas, Oklahoma and California. They would dwarf the earlier supplies.