The captains of the oil industry were among the most successful entrepreneurs of any century, reaping huge profits from oil, natural gas, and their byproducts and building business empires that soared to capitalism's heights. Oil even became a factor in some of the most complex geopolitical struggles in the last quarter of the 20th century, ones still playing out today.

Oil has touched all our lives in other ways as well. Transformed into petrochemicals, it is all around us, in just about every modern manufactured thing, from the clothes we wear and the medicines we take to the materials that make up our computers, countertops, toothbrushes, running shoes, car bumpers, grocery bags, flooring tiles, and on and on and on. Indeed, the products from petrochemicals have played as great a role in shaping the modern world as gasoline and fuel oils have in powering it.

It seems at first a chicken-and-egg sort of question: Which came first—the gas pump or the car pulling up to it? Gasoline was around before the invention of the internal combustion engine but for many years was considered a useless byproduct of the refining of crude oil to make kerosene, a standard fuel for lamps through much of the 19th century. Oil refining of the day—and into the first years of the 20th century—relied on a relatively simple distillation process that separated crude oil into portions, called fractions, of different hydrocarbon compounds (molecules consisting of varying arrangements of carbon and hydrogen atoms) with different boiling points. Heavier kerosene, with more carbon atoms per molecule and a higher boiling point, was thus easily separated from lighter gasoline, with fewer atoms and a lower boiling point, as well as from other hydrocarbon compounds and impurities in the crude oil mix.  Kerosene was the keeper; gasoline and other compounds as well as natural gas that was often found alongside oil deposits, were often just burned off.

Then in the first 2 decades of the 20th century horseless carriages in increasing droves came looking for fuel.  Researchers had found early on that the internal combustion engine ran best on light fuels like gasoline but distillation refining just didn't produce enough of it—only about 20 percent gasoline from a given amount of crude petroleum. Even as oil prospectors extended the range of productive wells from Pennsylvania through Indiana and into the vast oil fields of Oklahoma and Texas, the inherent inefficiency of the existing refining process was almost threatening to hold back the automotive industry with gasoline shortages.

The problem was solved by a pair of chemical engineers at Standard Oil of Indiana—company vice president William Burton and Robert Humphreys, head of the lab at the Whiting refinery, the world's largest at the time.  Burton and Humphreys had tried and failed to extract more gasoline from crude by adding chemical catalysts, but then Burton had an idea and directed Humphreys to add pressure to the standard heating process used in distillation.  Under both heat and pressure, it turned out that heavier molecules of kerosene, with up to 16 carbon atoms per molecule, "cracked" into lighter molecules such as those of gasoline, with 4 to 12 carbons per molecule, Thermal cracking, as the process came to be called, doubled the efficiency of refining, yielding 40 percent gasoline. Burton was issued a patent for the process in 1913, and soon the pumps were keeping pace with the ever-increasing automobile demand.

In the next decades other chemical engineers improved the refining process even further. In the 1920s Charles Kettering and Thomas Midgley, who would later develop Freon (see Air Conditioning and Refrigeration), discovered that adding a form of lead to gasoline made it burn smoothly, preventing the unwanted detonations that caused engine knocking. Tetraethyl lead was a standard ingredient of almost all gasolines until the 1970s, when environmental concerns led to the development of efficiently burning gasolines that didn't require lead. Another major breakthrough was catalytic cracking, the challenge that had escaped Burton and Humphreys. In the 1930s a Frenchman named Eugene Houdry perfected a process using certain silica and alumina-based catalysts that produced even more gasoline through cracking and didn't require high pressure. In addition, catalytic cracking produced forms of gasoline that burned more efficiently.