Harvard University World Religion Map, based on data from the World Religion Database.

The studies of China's Regional Religious System found "very high activity of popular religion and secret societies and low Buddhist presence in northern regions, while very high Buddhist presence in the southeast" (source).

Integrated with:

Hebei: Fieldwork by Thomas David Dubois (see The Sacred Village: Social Change and Religious Life in Rural North China, University of Hawaii, 2005) testifies the dominance of folk religious sects, specifically the Church of the Heaven and the Earth and the Church of the Highest Supreme, since their "energetic revival since the 1970s" (p. 13), in the religious life of the counties of Hebei. Religious life in rural Hebei is also characterised by a type of organisation called the benevolent churches, and the folk sect known as Zailiism has returned active since the 1990s.

Henan: Thomas Heberer, Sabine Jakobi. Henan - The Model: From Hegemonism to Fragmentism. Portrait of the Political Culture of China's Most Populated Province. Duisburg Working Papers on East Asian Studies, May 2000, n. 32.

As explained in the paper, Henan has been for centuries a hub of folk religious sects, which constitute significant focuses of the religious life of the province:

p. 7: "Early examples include the "Yellow Turbans" (huangjin), a messianist movement of Daoist inspiration in the 2nd century, and the "Red Turbans" (hongjin), a chiliastic movement awaiting the appearance of the Buddha Maitreya (Milefo) in the 14th century. In recent centuries this province was a major focal point of the "Sect of Heavenly Order" (tianlijiao), the White Lotus-sect, (bailianhui), the Nian-movement, the "Heavenly Bamboo-movement" (tianzhujiao), the "Society of Elder Brothers" (gelaohui), the "Green and Red Guild" (qinghongbang), the "Persistent Way" (yiguandao)-movement, the sect "Great King of Red Heaven" and the "Society of the Great Sword" (dadaohui), just to mention the most important ones."

Henan also has a strong Confucian orientation (p. 5).

Northeast China: According to official records by the then-government the Universal Church of the Way and its Virtue or Morality Society had 8 million members in the state of Manchuria, or northeast China, during Japanese occupation, making up about 25% of the total population of the area which at that time also comprehended the easternmost end of contemporary Inner Mongolia (see Ownby, 2008, Sects and Secularism in Reading the Modern Chinese Religious Experience). Folk religious sects of a Confucian nature, or Confucian churches, were indeed very successful in the northeast, gathering a large part of the population.

Shandong: Alex Payette's Local Confucian Revival in China: Ritual Teachings, ‘Confucian’ Learning and Cultural Resistance in Shandong. China Report, February 2016, vol. 52, no. 1, pp. 1-18. doi: 10.1177/0009445515613867.

Shandong is traditionally a stronghold of Confucianism and is the area of origin of many folk religious sects and Confucian churches of the modern period, including the Universal Church of the Way and its Virtue (万国道德会 Wànguó Dàodéhuì), the Way of the Return to the One (皈依道 Guīyīdào), the Way of Unity (一貫道 Yīguàndào), and others.