Cahokia Mounds, some 13 km north-east of St Louis, Mis­souri, is the largest pre-Columbian set­tle­ment north of Mex­i­co. It was occu­pied pri­mar­i­ly dur­ing the Mis­sis­sip­pi­an peri­od (800‑1400), when it cov­ered near­ly 1,600 ha and includ­ed some 120 mounds. It is a strik­ing exam­ple of a com­plex chief­dom soci­ety, with many satel­lite mound cen­tres and numer­ous out­ly­ing ham­lets and vil­lages. This agri­cul­tur­al soci­ety may have had a pop­u­la­tion of 10–20,000 at its peak between 1050 and 1150. Pri­ma­ry fea­tures at the site include Monks Mound, the largest pre­his­toric earth­work in the Amer­i­c­as, cov­er­ing over 5 ha and stand­ing 30 m high.