Isan has a number of important Bronze Age sites, with prehistoric art in the form of cliff paintings, artifacts and early evidence of rice cultivation.
Iron and bronze tools such as those found at Ban Chiang may predate similar tools from Mesopotamia.

The region later came under the influence of the Dvaravati culture, followed by the Khmer Empire.
The latter built dozens of prasats (sanctuaries) throughout Isan.
The most significant are at Phimai Historical Park and Phanom Rung Historical Park.
Preah Vihear Temple was also considered to be in Isan, until the International Court of Justice in 1962 ruled that it belonged to Cambodia.

After the Khmer Empire began to decline in the 13th century, Isan was dominated by the Lao kingdom of Lan Xang, which had been established by Fa Ngum.
Due to a scarcity of information from the periods known as the dark ages of Cambodia, the plateau seems to have been largely depopulated.
There were few if any lines of demarcation, for prior to the 19th century introduction of modern mapping, the region fell under what 20th century scholars called the "mandala system".
Accordingly, in 1718 the first Lao mueang in the Chi River valley — and indeed anywhere in the interior of the Khorat Plateau  — was founded at Suwannaphum District (in present-day Roi Et Province) by an official in the service of King Nokasad of the Kingdom of Champasak.

The region was increasingly settled by both Lao and Thai emigrants.
Thailand held sway from the 17th century, and carried out forced population transfers from the more populous left (east) bank of the Mekong to the right bank in the 18th and 19th centuries.
This became more severe following the Lao rebellion (1826–1828) for complete independence of 1826–9.
In the wake of the Franco-Siamese War of 1893, the resulting treaty with France and the Anglo-Siamese Treaty of 1909 made the plateau a border region between Thailand and the Laos of French Indochina.

In the mid-20th century, the state-supported assimilation policy called Thaification promoted the ethnic integration of Isan into the modern conception of Thai nationality and de-emphasized the use of ethnic markers, for ethnic Laos and Khmers, as it was deemed uncivilized and to prevent ethnic discrimination among the Thai people.

The national government claimed that the name "Isan" was derived from Sanskrit Īśāna, a name of Shiva they claimed referred to his rule of the northeast (Sanskrit īśānya).
This interpretation was intended to reinforce Isan's identity as the northeast of Thailand, rather than as part of the Lao kingdom which was recently created by the French colonial discourse, as "race was then an important ideological tool for French colonialists in the attempt to seize the 'Laotian' and 'Cambodian' portions of Siam."

Before the central government introduced the Thai alphabet and language in regional schools, the people of Isan wrote in the Lao alphabet, a very similar script that Thai adopted.
Most people speak Isan, a variety of Lao, as their first language.
A significant minority in the south also speak Northern Khmer.

The Kuy people, an Austroasiatic people concentrated around the core of what was once called "Chenla" and known as the Khmer Boran "ancient Khmer", are a link to the region's pre-Tai history.
Isan has a number of important Bronze Age sites, with prehistoric art in the form of cliff paintings, artifacts and early evidence of rice cultivation. Iron and bronze tools such as those found at Ban Chiang may predate similar tools from Mesopotamia.
The region later came under the influence of the Dvaravati culture, followed by the Khmer Empire. The latter built dozens of prasats (sanctuaries) throughout Isan. The most significant are at Phimai Historical Park and Phanom Rung Historical Park. Preah Vihear Temple was also considered to be in Isan, until the International Court of Justice in 1962 ruled that it belonged to Cambodia.
After the Khmer Empire began to decline in the 13th century, Isan was dominated by the Lao kingdom of Lan Xang, which had been established by Fa Ngum. Due to a scarcity of information from the periods known as the dark ages of Cambodia, the plateau seems to have been largely depopulated. There were few if any lines of demarcation, for prior to the 19th century introduction of modern mapping, the region fell under what 20th century scholars called the "mandala system". Accordingly, in 1718 the first Lao mueang in the Chi River valley — and indeed anywhere in the interior of the Khorat Plateau  — was founded at Suwannaphum District (in present-day Roi Et Province) by an official in the service of King Nokasad of the Kingdom of Champasak.
The region was increasingly settled by both Lao and Thai emigrants. Thailand held sway from the 17th century, and carried out forced population transfers from the more populous left (east) bank of the Mekong to the right bank in the 18th and 19th centuries. This became more severe following the Lao rebellion (1826–1828) for complete independence of 1826–9. In the wake of the Franco-Siamese War of 1893, the resulting treaty with France and the Anglo-Siamese Treaty of 1909 made the plateau a border region between Thailand and the Laos of French Indochina.
In the mid-20th century, the state-supported assimilation policy called Thaification promoted the ethnic integration of Isan into the modern conception of Thai nationality and de-emphasized the use of ethnic markers, for ethnic Laos and Khmers, as it was deemed uncivilized and to prevent ethnic discrimination among the Thai people.
The national government claimed that the name "Isan" was derived from Sanskrit Īśāna, a name of Shiva they claimed referred to his rule of the northeast (Sanskrit īśānya). This interpretation was intended to reinforce Isan's identity as the northeast of Thailand, rather than as part of the Lao kingdom which was recently created by the French colonial discourse, as "race was then an important ideological tool for French colonialists in the attempt to seize the 'Laotian' and 'Cambodian' portions of Siam."
Before the central government introduced the Thai alphabet and language in regional schools, the people of Isan wrote in the Lao alphabet, a very similar script that Thai adopted. Most people speak Isan, a variety of Lao, as their first language. A significant minority in the south also speak Northern Khmer.
The Kuy people, an Austroasiatic people concentrated around the core of what was once called "Chenla" and known as the Khmer Boran "ancient Khmer", are a link to the region's pre-Tai history.
Isan