Native Hawaiian religion governed the islands for centuries through the kapu system, a comprehensive set of sacred restrictions enforced through the heiau, temple platforms built across the islands, many of which still stand today as protected historic sites. The kapu system regulated nearly every aspect of daily life, from what could be eaten together to who could approach whom, and its violation carried consequences the tradition treated as both social and cosmological. In 1819, before any Christian missionary had yet arrived, King Kamehameha II and the powerful chiefess Kaahumanu formally abolished the kapu system themselves, an internally driven religious rupture that left the islands without their traditional sacred order for roughly a year before anything replaced it.
The first Congregationalist missionaries from New England arrived in 1820, stepping directly into that vacuum, and built the islands' first Protestant churches while also reducing the Hawaiian language to written form for the first time, work that simultaneously preserved the language and became a tool for the political and land dispossession Native Hawaiian sovereignty movements continue to contest today. Japanese immigration in the late nineteenth century then added an entirely separate religious layer, bringing Buddhist temples and Shinto shrines that remain active across the islands. Between a suppressed but not extinguished Native Hawaiian tradition, missionary Protestantism, and transplanted Japanese Buddhism and Shinto, Hawaii carries one of the most religiously layered histories of any state, matching Pew's own finding that no single named tradition claims even a quarter of its adults today.