Korea's literate religious record is Buddhist and Confucian, and it is substantial. Monastic and court documents run deep, the Tripitaka Koreana survives as one of the great achievements of East Asian printing, and the Joseon dynasty's adoption of Confucian orthodoxy produced five centuries of state ritual documented in detail.
The indigenous practice usually called musok sits almost entirely outside that record. It was carried mainly by women, mostly in households rather than institutions, and by practitioners who did not write. For most of the Joseon period it was disparaged by the literate class, so the sources that mention it are dismissive and thin.
The first systematic descriptions come from the colonial period, when Japanese scholars conducted ethnographic surveys of the peninsula. Those surveys preserve a great deal and they were made by an administration with an interest in classifying its subjects, which is a familiar difficulty in this atlas.
The twentieth century then cut the record twice. Colonial rule imposed State Shinto observance, and the division of the peninsula after 1945 placed part of the population under a government that suppressed religious practice generally. Study of the northern half is largely study of the past.
In the south, musok has since become both a living practice and an object of heritage designation, and some of what is now performed has been shaped by that recognition. Distinguishing the two is an active scholarly problem.