With the merger of Exxon and Mobil in 1999, the newly formed Exxon Mobil Corporation brought together a shared history that dates back over 120 years to their origins as part of the Standard Oil family of companies.

John D. Rockefeller and partners formed the Standard Oil Company of Ohio in 1870, after having entered the oil business in 1863 with the founding of Andrews, Clark & Company and later Rockefeller, Andrews & Flagler in 1867. Standard Oil quickly began partnering with or purchasing many other Northeastern companies responsible for refining, transporting and marketing petroleum products. In 1882, after determining the feasibility of setting up a joint-stock corporation, Rockefeller and partners formed the Standard Oil Trust to unify what then numbered about 40 companies. From then on, the Trust's nine trustees exercised broad management and control for each company, with daily operational decisions made at the individual company level. That same year, the Trust formed Standard Oil Company of New Jersey and Standard Oil Company of New York, which soon became two of the Trust's larger concerns.

By 1889, the Trust had amassed companies responsible for all aspects of the petroleum industry - exploration, production, refining, transportation and marketing - creating a vertically integrated organization. Congress's passage of the Sherman Anti-Trust Act of 1890, however, which aimed to ensure fair competition in interstate commerce and to eliminate monopolies, eventually led to the dissolution of the Trust in 1892.

Not to be outdone, the company rebounded by forming the Standard Oil Interests, consisting of about 20 holding companies. In 1899, taking advantage of a New Jersey law allowing a single corporation to own stock in other companies, Standard Oil Company of New Jersey became the holding company for the Standard Oil Interests.

A year earlier, however, the Ohio attorney general had begun legal proceedings to order all Ohio companies affiliated with Standard Oil to separate and begin operating independently. Other states soon followed, with charges that Standard Oil continued to violate anti-trust laws. In May 1911, after years of legal proceedings, the United States Supreme Court declared Standard Oil Company of New Jersey an "unreasonable" monopoly and ordered it to dissolve, resulting in 34 distinct and separate companies.

The re-organized Standard Oil Company of New Jersey and Standard Oil Company of New York emerged as two of the strongest companies. (The former would become Exxon; the latter Mobil.) Throughout the 20th century, both companies continued to grow and forge individual identities. This growth meant strengthening its industry alliances, merging with other companies, developing new technologies and diversifying its holdings.

Both companies weathered the breakup well. Provisions of the 1911 dissolution agreement assigned marketing for New York state and New England to Standard Oil Company of New York (Socony) and allowed Socony to maintain its extensive overseas operations. Standard Oil (New Jersey) maintained marketing in the mid-Atlantic region and gained control of Standard Oil Company of Louisiana (Southern marketing), Carter Oil Company (production), Imperial Oil Company (Canadian operations) and Gilbert & Barker Manufacturing (service station equipment).

The companies' first major expansion was in the southwest. With oil discovered in Corsicana, Texas, as early as 1894, this was a logical region for exploration. Texas-based Magnolia Petroleum Company experienced rapid growth during the 1910s and quickly caught Socony's attention, resulting in substantial stock acquisitions. By 1925, Magnolia's stock was exchanged for Socony stock, and Socony's Texas properties were transferred to the newly incorporated Magnolia.

With Magnolia as a full-fledged subsidiary, Socony continued its growth by merging with Vacuum Oil Company of Rochester, New York, in 1931 to form the Socony-Vacuum Oil Company, Inc. The Standard Oil Company of Ohio had acquired majority interest in Vacuum Oil in 1879, and it was yet another strong company to emerge from the 1911 breakup. Organized in 1866,Vacuum Oil produced the first petroleum-based lubricants for horse-drawn carriages and, later, for steam engines. Notably, Vacuum Oil introduced the Mobil brand, which Socony-Vacuum continued to use.

As the merger provided increased stability in the domestic market, Socony-Vacuum set its sights on its foreign resources and joined with Standard Oil (New Jersey) to form the Standard-Vacuum Oil Company, or Stanvac, in 1933. This 50/50 venture operated in nearly 50 countries, from Africa to the South Pacific, until the assets were divided in 1962.

Just as Socony expanded into the southwest, Standard Oil (New Jersey), too, sought to take advantage of new opportunities in the region and entered Texas soon after Socony, acquiring Humble Oil & Refining Company in 1919. Standard Oil continued to build its interest in Humble throughout the first half of the century. By 1958, Standard Oil owned nearly 98% of Humble. The next year Standard Oil and Humble consolidated their U.S. operations. By the end of 1960, Humble had absorbed Esso Standard (Standard's domestic operating company), Carter Oil Company, Enjay Chemical Company, Oklahoma Oil Company and other Standard Oil affiliates, resulting in a more streamlined and efficient company.

During World War II, major oil companies stepped up production and refining to support the war effort. Unfortunately, both companies experienced casualties as facilities and tankers were destroyed in the European and Pacific theaters. When the war ended, the companies looked toward rebuilding and again expanding their markets. In 1948, Standard Oil (New Jersey) and Socony-Vacuum collaborated again, joining with Texaco and the Standard Oil Company of California in the Arab-American Oil Company (Aramco) venture in Saudi Arabia, marking their first significant presence in the Middle East.

Socony-Vacuum reorganized in 1955 to become the Socony Mobil Oil Company, Inc. Further consolidation occurred in 1959, when Magnolia Petroleum Company, as well as General Petroleum Corporation (a California-based affiliate) and Mobil Producing Company (a Socony Mobil subsidiary) began operating as the Mobil Oil Company, a wholly owned subsidiary of Socony Mobil. A decade later, with increased brand recognition for Mobil products, Socony Mobil opted to once again change its name, this time becoming simply the Mobil Oil Corporation.

In 1959, Standard Oil (New Jersey) discovered oil in Libya, setting off a decade of major discoveries in the Middle East. Standard Oil established itself as a global chemical producer in 1965, following the formation of Mobil Chemical Company in 1960.

The 1970s proved to be a period of great change for both companies. Standard Oil started the decade contemplating its corporate identity. Throughout Standard's partnership with Humble, they marketed products under various names, using Esso (the phonetic spelling of the abbreviation "S.O.") on the east coast, Humble in Texas and Ohio, and Enco (short for "Energy Company") in 19 other states. The existence of other "Standard Oils" around the country - California, Indiana, Ohio, to name a few - made it necessary to use these different brand names in different regions. Citing the need for uniformity among its products, Standard Oil (New Jersey) announced in 1972 that it would market its products under the brand name "Exxon;" Standard Oil Company of New Jersey would become Exxon Corporation; and Humble Oil & Refining Company would become Exxon Company, U.S.A., the domestic arm of the Corporation. Outside the U.S., products would still carry the Esso name.

A big challenge to the oil industry came in 1973 with the Arab oil embargo, with countries disrupting production, causing oil supplies to diminish and prices to soar. This event forced Exxon and Mobil to increase exploration and production in other parts of the world, including the North Sea, the Gulf of Mexico, Africa and Asia. As a result of the energy crisis, Mobil began seriously diversifying its holdings, acquiring Marcor, the parent company of retailer Montgomery Ward and Container Corporation of America, producer of paperboard packaging. Later, in 1976, Mobil Corporation formed as a holding company for Marcor and Mobil Oil Corporation, which included the company's oil and gas operations and Mobil Chemical Company.

The 1980s and 1990s marked a period of relative prosperity for Exxon and Mobil, with increased oil supplies and reduced prices. This period also saw the introduction of new marketing techniques, such as Exxon's Tiger Market convenience stores and Mobil's Speedpass technology. By 1999, Exxon and Mobil were poised to merge and become the world's largest energy corporation.