The oldest known iron smelting site in Thailand is located in San Huey Tok Hin, Lumphun Province and dates to 8th century AD. The latest iron smelting site is Muang Long Ancient city (Ban Na Tum Archaeological Site) dating around 19th - 20th century AD. Historical evidence from this period indicates that Maung Long city provided 2400 kg of iron as tribute to the ruler of Maung Lampang every year. The Smelting process was undertaken at what is now the Ban Na Tum Archaeological site. The iron ore (haematite) was transported to Ban Na Tum over 1 km from a mine local inhabitants call ‘Doi Lek (the mountain of iron). At Ban Na Tum the ore was smelted in a furnace structure 80 cm high using a double piston bellow system, and the ‘direct process’ which required temperatures of approximately 1100 – 1200 Celsius degree. Direct dating of carbon recovered from slag cake by the Fine Arts Department of the Chiang Mai Province produced a date of 202±16 years ago, confirming that the furnace was active during the 19th century. Chinese ceramic found near the furnace manufactured during the Qing Dynasty also supports a 19th - 20th century date. The iron ingots produced at Ban Na Tum (or Maung Long) were of high quality and very expensive in Northern Thailand during 19th - 20th century. The costumer always comment that “The best quality iron was produced at Muang Long!, And the best quality gold is from Maung Phayao!”. Moreover, some literature from Northern Thailand such as “The poem of the ruler of Maung Phrae’s palace celebration; Sriwijai 1832 AD” describes iron from Maung Long as not only strong, but also sacred.