The Ping River Valley was long a trading route between Yunnan and the Chao Phraya basin. Evidence from archeological remains has shown that early inhabitants used iron tools in the valley at least two thousand years ago. These early people, who came to be known as the Lawa, were later supplanted by the Mon of the Dvaravati period (6- 10th centuries). Drawn by trade along the river, the Mon chose the wide, fertile valley to found Haripunchai (Lamphun), in the eighth century. It was the first city-state with a "high culture" in the valley.