The Magnolia Petroleum Company, founded as an unincorporated joint-stock association on April 24, 1911, was a consolidation of several earlier companies, the first of which, the J. S. Cullinan Company, began operating a refinery at Corsicana, Texas, on December 25, 1898. The Corsicana Petroleum Company, planned as a crude-oil producer for the Cullinan plant, was organized in 1899. The George A. Burts Refining Company, organized in 1901 to absorb much of the crude oil from the Spindletop oilfield, became the Security Oil Company. In 1909 both the Navarro Refining Company, successor to the Cullinan Company, and the Security Oil Company were purchased by the John Sealy Company, which in 1911 became the Magnolia Petroleum Company, with Sealy as president (see SEALY, JOHN HUTCHINGS).
The Magnolia Company was originally capitalized at $2,450,000–24,500 shares at $100 each. In 1925 the company purchased the Corsicana Petroleum Company. Capitalization was $185 million in 1925. As Magnolia Petroleum Company became increasingly important in the southwestern states, the Standard Oil Company of New York began acquiring some of its stock. In December 1925 all of the Magnolia stock was exchanged for Standard Oil Company of New York stock, and the Texas properties were transferred to Magnolia Petroleum Company, chartered under Texas law on November 21, 1925, as a corporation to replace the former joint-stock association. The Magnolia Pipe Line Company was organized in November 1925, as a transporting subsidiary of the petroleum company. In 1931, when the Standard Oil Company of New York and the Vacuum Oil Company merged to form Socony-Vacuum Oil Company, Magnolia became an affiliate of the new company.
In 1949 Magnolia had a capitalization of $125 million, all shares owned by Socony-Vacuum except for qualifying shares owned by members of Magnolia's board of directors. Magnolia Pipe Line Company was capitalized at $16.5 million, its stock being owned by Magnolia Petroleum Company except for qualifying shares held by directors of the pipeline company. Gross fixed assets of the company on December 31, 1948, were nearly $700 million, including the assets of the pipeline company, which had 8,670 miles of pipeline extending into nine states. General offices were in Dallas in 1949, when the company had permits to do business in twenty states and had some 12,500 employees. The Magnolia Petroleum Company merged with Socony Mobil Oil Company on September 30, 1959. Its operations became part of Mobil Oil Company, which had been formed in March 1959 as an operating division of Socony Mobil, responsible for all operations except marine transportation in the United States and Canada. Magnolia Pipe Line Company was not absorbed into Mobil Oil Company but remained a common carrier affiliate of Socony Mobil.