东光县 / Dongguang County (late Han)
东光县 / Dongguang County (late Han) enters the wiki through Hanji 958 as the area south of which 公孙瓒 attacks the 青州黄巾军. The source says he uses a much smaller steppe-and-cavalry force to defeat a large Yellow Turban movement preparing to link with the 黑山军.
The place matters because it is the first visible accelerator in the episode. Gongsun Zan’s victory, captures, and equipment gains make him a larger regional actor before the later 袁绍 rivalry and 刘虞 rupture become central.