Mexico's taking control of its oil sector from U.S. and British companies is taught in schools and celebrated every year. The 1938 nationalization is a point of pride for millions of Mexicans including President Andrés Manuel López Obrador.

The popular president hails from the Mexican oil industry's heartland, and 16 years ago he led a fight against energy reforms that were aimed at drawing private investment to the massive state-run oil company, Pemex. This year, the front-runner in the race to replace López Obrador chose the anniversary of Mexico's oil expropriation to announce her energy proposals, which include maintaining large-scale petroleum production by Pemex.