Buddhism was introduced to Korea in the 4th century. It soon became a dominant religion in the southeastern kingdom of Silla, the region that hitherto hosts the strongest concentration of Buddhists in South Korea. In the other states of the Three Kingdoms Period, Goguryeo and Baekje, it was made the state religion respectively in 372 and 528. It remained the state religion in Later Silla (North South States Period) and Goryeo. It was later suppressed throughout much of the subsequent history under the unified kingdom of Joseon (1392–1897), which officially adopted a strict Korean Confucianism. Today, South Korea has about 7 million Buddhists, most of them affiliated to the Jogye Order. Most of the National Treasures of South Korea are Buddhist artifacts.