Sangju is nicknamed Sam Baek, or "Three Whites", referring to three prominent agricultural products rice, silkworm cocoons, and dried persimmons from the area.

It first emerges after the Silla conquest of the area, in which minor states such as Goryeong Gaya (in Hamchang-eup) and Sabeol-guk (in Sabeol-myeon) were subjugated.

The dates at which these conquests occurred are open to dispute, but it is apparent that the area was under firm Silla control by 505, and probably for some time before then.

Under Silla, the fortress of Sangju was one of the nine ju, or provincial administrative units, into which the portions of the kingdom near Gyeongju were divided.

It played a critical role in regulating traffic along the east–west transit route which connected the Han River valley in the west (which Silla acquired in 553) with Gyeongju area.

It would have been the first major city that Buddhist missionaries from Goguryeo would have reached when travelling down from Haneuljae Pass in the 6th century.

During the tumultuous decline of Unified Silla in the late 9th century, a number of rebellions occurred in Sangju, as they did throughout the country.

Notable among them are the rebellions of Ajagae, who seized the fortress of Sangju and declared himself a general, and the Silla noble Bak Eon-chang, who re-established the kingdom of Sabeol-guk in the Sabeol-myeon area until he was overthrown by the Later Baekje leader Kyŏn Hwŏn.

One member is elected from each eup, myeon, and dong, except for Sinheung-dong and Dongseong-dong, which share a single representative.

Currently 243,000 m2 (2,615,630 sq ft) of land are engaged in silk production, bringing in about 434 million won annually.

Sangju today is an important regional center of industry and commerce as well, exerting a significant economic effect on neighboring areas.

Also, Sangju tries to keep up agaricultural section with some specialized and traditional produces such as dried persimmon and fruits raised in high altitude.

From west to east along the city's northern border, the myeon are Hwabuk-myeon, Oeseo-myeon, Euncheok-myeon, and Ian-myeon which adjoins Hamchang-eup.

From east to west along the southern border are Cheongni-myeon, Gongseong-myeon, Modong-myeon, and Moseo-myeon in the southwest corner.

They are Bukmun-dong in the northern part of town, Gyerim-dong in the northeast, Dongmun-dong to the east, Dongseong-dong to the southeast, Sinheung-dong to the south, and Namwon-dong to the west.

The Gyeongbuk Line carries both passenger and freight traffic, and provides an important link for people and businesses in the hinterland of Sangju.

For example, National Road 3 has served as the traditional artery connecting Sangju with Mungyeong and Chungju, and National Road 25 continues to play an important role tying Sangju to its neighbor on the western side of the Sobaek mountains, Boeun County.

Like the rest of South Korea, Sangju has a three-tiered system of education: elementary, middle, and high.