It was originally called 'Gaecheon(Hangul:개천, Hanja:開川 ).' The Cheonggyecheon used to be a naturally formed stream before the Joseon Dynasty designated Seoul as its capital. This stream caused a flood and inundated private houses in full spate. In ordinary times, it was unsanitary because of standing sewage therein. Therefore, King Taejong, the third king of the Joseon Dynasty, firstly beginned river training work by starting construction work for an open channel. After that, King Yeongjo, the 21st king of the Joseon Dynasty, conducted the overhaul of the stream in earnest by dredging the stream, building stone banks and changing a waterway. Due to this construction, the curved waterway of the stream became straight one at last. During the reign of King Sunjo and King Kojong, the overhaul of the stream was continued. There were 24 bridges over the stream(now 22 bridges).