A map of the Olmec heartland. The yellow sites are known villages and towns.  The smaller red dots mark locations where artifacts or art have been found unassociated with habitation.
Own work using:

Coe, Michael; Snow, Dean; Benson, Elizabeth; (1986) Atlas of Ancient America; Facts on File, New York, pp. 94-95.
Coe, M.D. (2002) Mexico: From the Olmecs to the Aztecs London: Thames and Hudson; pp. 64, 75-76.
Diehl, Richard A. (2004) The Olmecs: America's First Civilization, Thames &amp; Hudson, London, p.12.
No machine-readable author provided. Madman2001 assumed (based on copyright claims).