This paper describes 15 stone monuments documented until the 1995 field season at Río Viejo, the largest settlement in the alluvial plains of the Río Verde drainage in Coastal Oaxaca from 100 B.C. to A.D. 1100. The monuments, all seemingly dating to the Classic period (A.D. 600–900), include mainly carved stelae that most often depict elaborately dressed human figures accompanied by their calendrical names. The large size of these monuments and the political primacy of Río Viejo strongly suggest that the named individuals were local rulers. We posit that additional flattened sculptures and slabs riddled with small circular depressions were foci of sacred activities aimed at petitioning favors from supernatural forces. The analysis of the inscriptions is framed in terms of graphic similarities with highland scribal traditions in the central valleys of Oaxaca, the Mixteca Baja, and the Mexican Highlands.