The Bronze Age in Korea is often held to have begun around 900–800 BC in Korea, though the transition to the Bronze Age may have begun as far back as 2300 BC. Bronze daggers, mirrors, jewelry, and weaponry have been found, as well as evidence of walled-town polities. Rice, red beans, soybeans and millet were cultivated, and rectangular pit-houses and increasingly larger dolmen burial sites are found throughout the peninsula.Gochang, Hwasun and Ganghwa Dolmen Sites , UNESCO Contemporaneous records suggest that Gojoseon transitioned from a feudal federation of walled cities into a centralised kingdom at least before the 4th-century BC. It is believed that by the 4th century BC, iron culture was developing in Korea by northern influence via today's Russia's Maritime Province.Wontack Hong, "The Yemaek Tungus of Central Manchuria and Korean Peninsula: Interactions between the Xianbei and the Yemaek Tungus"
