U Thong district

Walailak Songsiri treats the ancient city as one of a cluster of early sites in the basins of the Chorakhe Sam Phan, which gave the district its first name, and the Tha Wa, the others being Don Ta Phet in the neighbouring Phanom Thuan district, Na Lao and Suan Taeng. On her account the group was already occupied in the pre-Dvaravati period conventionally called the Funan period, and the trade in tin, lead, silver and iron from the Tenasserim range was developed before the 13th century.^[3]: 1

Higham states, "U-Thong was occupied for many centuries prior to the development of the Dvaravati state. Radiocarbon determinations from the sites of U-Thong and Chansen suggest that the transition into complex state societies in the Chao Phraya basin took place between about 300–600 AD." A copper inscription from the mid-7th century states, "Sri Harshavarman, grandson of Ishanavarman, having expanded his sphere of glory, obtained the lion throne through regular succession," and mentions gifts to a linga. The site includes a moat, 1,690 by 840 m, and the Pra Paton caitya.^{[2]: 300, 302, 306–307}

It also became the origin of the Ayutthaya Kingdom, as the first King of Ayutthaya, Ramathibodi, was prince of U Thong when the city was struck by an epidemic, prompting him to relocate east and found Ayutthaya.^[4]

U Thong district was created with the name Chorakhe Sam Phan in 1905. In 1939 the district was renamed U Thong.^[5] In 1944, the government moved the centre of the district from Ban Chorakhe Sam Phan to the area of the ancient city.^[6]

Neighbouring districts are (from the north clockwise): Don Chedi, Mueang Suphan Buri, Bang Pla Ma, Song Phi Nong of Suphan Buri Province; Lao Khwan, Huai Krachao, and Phanom Thuan of Kanchanaburi province.