In the southernmost Brazilian port of Rio Grande, coastal reclamation actions for land expansion seaward have been going on for nearly 300 years. Mercury contamination of man-made–ground deposits was detected at all coastal reclamation sites. For most polluted sites, the mercury concentration was up to 300 times higher than the local background concentration. Use of city waste and garbage for coastal reclamation is the main source of mercury pollution. In the 18th and 19th centuries, the most significant source of mercury was the felt manufacture wastes. In the 20th century, sources of mercury in city garbage were more diverse, with mercury-based medicaments probably contributing significantly. Heavily polluted deposits represent sources of secondary mercury contamination for nearly all components of the coastal environment: sediment, air and atmospheric deposits, fish, and vegetation.