Flix was the site of a battle in the Spanish Civil War in 1938. The Battle of the Iron Bridge was fought between the International Brigades and the Fascists as part of the Battle of the Ebro. The operation was initially a success for the republicans with the construction of the iron bridge nearly complete by the 3rd Division. However at the end they had lost 3,000 soldiers and the battle. Today there is a memorial to this battle at Flix.
In 2005 the existence of a vast polluted area on the shores of the Flix Reservoir was disclosed. The environmental disaster involving large quantities of toxic waste was caused by the Ercroschemical factory, located by the shore of the artificial lake. Following this disclosure an ambitious plan to clean up the area has been drawn. This plan involves the building of containment barriers and the removal and treatment of the hazardous chemical waste.