The history of Pematangsiantar is closely intertwined with the culture of the Batak Simalungun people and Indonesia's colonial past. The city has evolved from the capital of an ancient kingdom into a major economic center of North Sumatra.
Originally, Pematangsiantar was the capital of the Kingdom of Siantar—one of several Simalungun kingdoms where power was held by the Damanik dynasty. The exact date of the city's founding is unknown, as it developed as the residence of the local ruler (Raja). The first written mentions of the "Siantar" region date back to the early 19th century, when British explorers described the local principalities.
A turning point in the city's history came at the beginning of the 20th century when the region came under the control of the Dutch colonial administration. Recognizing the potential of the fertile land, the Dutch began actively developing rubber, tea, and oil palm plantations here. In 1907, Pematangsiantar became an administrative center, and in 1917, it was granted municipality status (gemeente), which accelerated its growth. The construction of roads connecting the city with the major port of Medan transformed it into an essential trading hub.
In the pre-colonial period, the city's culture was entirely based on Simalungun traditions. However, with the arrival of the Dutch and the development of the plantation economy, the economic and social landscape shifted. Labor was brought in from other regions, particularly from the island of Java, making Pematangsiantar a multi-ethnic city. The economy, previously focused on local agriculture, shifted to the production of export goods, facilitating the city's growth and modernization.