The principal dialect of the province is Ilocano representing about 95% of the total population of 658,587 in 2010. Other dialects/languages spoken in the province include Tagalog, Pangasinense, Visaya, Chinese, English, Kankanai, Tinggian and Muslim.
Christianity is widely spread in the province. Approximately 85 percent of the total population professes Roman Catholicism, the prevailing religion in the province. The remaining percentage of the population professes to Protestantism, Buddhism, Iglesia Ni Cristo, Aglipayan, Islamism, Jehovah’s Witnesses, Seventh Day Adventists and Born Again Christians.