The Chamorro people of the Marianas honoured the aniti, the spirits of ancestors whose skulls were kept in homes and consulted by the makana, and respect for the taotaomona, the people of before who inhabit the banyan trees, still governs behaviour in the jungle: one asks permission before entering their places. Spanish Catholicism arrived with sails and cannon.
The Jesuit Diego Luis de San Vitores founded the Marianas mission in 1668 and was killed at Tumon in 1672 after baptising a chief's daughter against her father Matapang's will; he was beatified in 1985, and the wars and epidemics that followed his mission devastated the Chamorro population, which rebuilt itself inside the church. Three and a half centuries later Catholicism is inseparable from Chamorro culture: each village keeps its patron's fiesta with processions and communal tables, novenas are led by the techa, the lay prayer leaders who kept the faith alive when priests were scarce, and the nobena and rosary for the dead anchor family life.
The Japanese occupation of 1941 to 1944 made the faith a resistance identity, its priests imprisoned and its statues hidden. The American decades brought Baptist, Adventist and Pentecostal churches, and Guam's religious profile now resembles a Pacific Catholic heartland with a Protestant fringe, the whole island still pausing each 8 December for its Lady.