The people who had made 'plain coarse pottery' with montmorillite clay had shared common techniques in making pottery, although their locations are ranged within one hundred km distances along the Yeongson River Valley in Korea. They shared common phenomenal characteristics such as dolmens and subterranean settlements and lived on rice cultivation, but the results of technical analyses can add other evidence that they had shared common techniques in making potteries and had taken part in the interregional trade system based on the specialization; and, so those sites can be included in the Yeongsan River Valley Culture during the late bronze age or early iron age.