Like many revered Buddha images, the Emerald Buddha has a mysterious past. Nobody knows when or where it was made, although it is stylistically similar to images popular in northern Thailand. The image was discovered in 1434 when lightening cracked open a chedi in a Chiang Rai temple now also known as Wat Phra Kaeo. When discovered, it was covered in plaster and the abbot of the temple kept it in his quarters until the plaster started to flake off, revealing the jade underneath.
Hearing of the discovery, the King of Lanna dispatched some soldiers to bring the image back to Chiang Mai. However, the elephant sent to carry the image refused to take the road back to Chiang Mai (Buddha images are often thought to have such powers over their movement). Seeing this, the escort took it as a sign and re-routed to Lampang.
Eventually, a later king seems to have 'convinced' the image to come to Chiang Mai, where it was enshrined in Wat Chedi Luang. But in 1552 the line of Lanna kings was interrupted and filled by the crown prince of Laos. However, after just a short time he returned to Luang Prabang to take the throne, taking the Emerald Buddha with him. The image was later moved to the new Lao capital of Vientiane, where it stayed for more than 200 years.
In 1778, while in the process of reuniting Siam after the sacking of Ayutthaya, King Taksin dispatched General Chakri on a punitive expedition to Laos, where he took Vientiane in 1779. Chakri bought the Emerald Buddha back with him, and when he later became King Rama I, he built the temple to house the image.