Here Joshua had called all the tribes together for a covenant renewal ceremony at the completion of his campaigns of conquest (Joshua 24:1), and it lay at the southern end of the valley separating Gerizim and Ebal, the mountains of covenant blessing and curse, respectively (Deuteronomy 11:29). So it was a place of huge symbolic importance. It had already emerged as a place of potential significance for the present narrative from the fact that Gideon had had a concubine there, and that Abimelech was his son by her (Judges 8:31).1
6 And all the leaders of Shechem came together, and all Beth-millo, and they went and made Abimelech king, by the oak of the pillar at Shechem.