World War II

Indiana Standard participated in the war effort, discovering new means of refinement and even a way of producing TNT quickly and easily. It also significantly contributes to the aviation fuel needs of the Allied forces. A chemical division was created which was formed from the merger of the Pan American Chemicals and Indoil Chemicals.
After the World War II, Indiana Standard returned to focusing on domestic oil refinement. In 1947 Indiana Standard was the first company to drill off-shore, in the Gulf of Mexico, and in 1948 the company invented Hydrafrac,  a hydraulic well fracturing process that increased oil production worldwide.

In 1956, the Pan-American stations in the southeastern U.S. were rebranded as Amoco stations. In 1961, Indiana Standard reorganized its marketing giving its American Oil Company unit responsibility for its retail operations nationwide under the Standard name inside the Indiana Standard marketing area and under the American name outside that region. Both brands shared the same redesigned torch and oval logo for easy identification throughout the US. The Amoco name continued to be used outside the U.S. and as a brand on certain American Oil products.

Soon, the company began to expand. With an exploration office in Canada, Indiana Standard was now a recognized international oil and gas player. Indiana Standard bought and created several new plants and claimed various new oil fields in this time period, as the company prospered in the post-war boom.

By 1971, all the divisions of Indiana Standard bore the Amoco name including American Oil which was renamed Amoco Oil with American stations renamed Amoco stations. By 1975, Amoco began phasing in the Amoco name in the old Indiana Standard sales territory. Standard Oil Company (Indiana) was officially renamed Amoco Corporation in 1985.