The development of the petroleum industry in Mexico on the Gulf Coast dates from the late nineteenth century. Two prominent foreign investors were Weetman Pearson, who was later knighted by the British crown, and Edward L. Doheny, as well as Rockefeller's Standard Oil. Oil has been an important contributor to the Mexican economy as well as an ongoing political issue, since early development was entirely in the hands of foreigners. Economic nationalism played the key role in the Mexican oil expropriation of 1938.