Chiang Mai Zoo was established by Mr. Harold Mason Young, an American missionary who volunteered to teach forest survival guide to soldiers and policemen at borderland during Korean War (1950-1953). At the beginning, He used the rented house, owned by Mr. Kee Nimmanhaemin (1888-1965) and Mrs. Gimhor Nimmanhaemin (1894-1981), that he lived at the moment called "Weluwan House” located at the foot of Doi Suthep. He opened a small private zoo for the first time around 1952 and hired few local people and tribesmen to take care of the zoo.

Although the reason who Mr. Harold Mason Young had collected so many kinds of animal that he can establish a private zoo is not clear, we believe it is that due to his fondness for animal and his intention to study animal behaviour closely to favor his career as the volunteer to teach forest survival guide to soldiers and policemen at borderland who will have to face various kind of animal all the time.

Mr. Harold Mason Young is a son of American missionaries. He was born at Shan State in Myanmar and used to work as a missionary in Shan State, the land of Tai people that filled with various kind of animals. The reason why Mr. Harold Mason Young have to work as a volunteer to teach forest survival guide to soldiers and policemen at borderland in Thailand may be due to the commitment that US Government had with Government of Thailand to give supports in terms of politic, military, economic and society, etc. in order to fight against communists together according to 3 Thai-American Covenants which are: Educational and Cultural Agreement, July 1950; economic and technical cooperation agreement, September 1950; and Military Aid Agreement, October 1950 onwards./p>

Since after 1950 US Government had sent a lot of consultants, volunteers and supporting forces into Thailand. In terms of soldier and police, the USA had sent Military Assistance Advisory Group (MAAG) to base in Thailand in 1950. Later the Group was expanded into JUSMAG to help planning to organize brigade, arrange mixed department, manage system, send military force, etc. At the same time, the police force which was led by Police General Phao Sriyanond had been expanded widely. US Government had given supports through Sea Supply Corporation, so when Mr. Harold Mason Young came to work in Thailand as a volunteer to teach forest survival guide to soldiers and policemen at borderland in Thailand, it should be in this political context as well.

The animal collections that Mr. Harold Mason Young have around Weluwan House where he rented must have kept increasing and require a larger area in the house. The beautiful area of Weluwan House, such as grass field in the front yard was used for keeping animal eventually.

According to Professor An Nimmanhaemin, an heir of Mr. Kee – Mrs. Gimhor Nimmanhaemin, he had asked Mr. Harold Mason Young, the tenant of Weluwan House, to move his zoo to another plot of land of Mr. Kee -Mrs. Gimhor Nimmanhaemin which also locates at the foot of Doi Suthep, being a part of Chiang Mai University nowadays. However, since Mr. Harold Mason Young is a citizen of America, a very influential country in the world, he had seek permission directly from Chiang Mai Governor to utilize reserved forest area at the foot of Doi Suthep. He finally obtained the permission to utilize reserved forest area at the foot of Doi Suthep, sized 60 Rai, as the location of the private zoo. The zoo was open from 6 April 1957 until Mr. Harold Mason Young passed away in 1975.

Chiang Mai Provincial Administrative Organization sees the value of Mr. Harold Mason Young’s zoo both as a place for relaxation and studying animal of people in Chiang Mai Province and as a tourist attraction according to the project to develop Doi Suthep into a place for relaxation. Therefore, Chiang Mai Provincial Administrative Organization has taken care of the zoo of Mr. Harold Mason Young.

Until 1977, the zoo was transferred to be under Zoological Park Organization of Thailand, Office of the Prime Minister from 16 June 1977 onwards. On 16 June 1987, Chiang Mai Zoo was 10 years old and in the decade the area of Chiang Mai Zoo has been expanded from 60-Rai area that Chiang Mai Province had permitted Mr. Harold Mason Young to utilize to 130-Rai area. From 1983, Chiang Mai Zoo was approved by Department of Forestry, Ministry of Agriculture and Cooperatives and the cabinet to expand the area at the foot of Doi Suthep for 500 Rai in addition. The Zoo Promotion and Improvement Committee was established. It consists of expert and professional from both government and private sectors and Professor An Nimmanhaemin was the chairman to set out the main plan and initiate the development roadmap of Chiang Mai Zoo in the future. According to historical evidences which are legends, records and aerial photograph, it is confirmed that a part of Chiang Mai Zoo is a part of Wiang Chet Lin, an circular ancient city built in the era of Phaya Sam Fang Kaen, the 8th King of Mangrai royal family (1945-1984). The trace of some canal and earthen dyke can still be seen. Nowadays many debris of bricks are generally seen around Chiang Mai Zoo, especially on the hill over the elephant zone there is a pile of large bricks which can be assumed that it is an ancient place related to religion (which is the location of Wat Ku Din Khao in present day.)