Islam, which was introduced in the 12th century, is followed by about about 90%. The main Muslim branches are Tijaniyah, Qadiriyah, Muridiyah, and Ahmadiyah. Christians (9%), mostly Roman Catholics, are concentrated in the Banjul area. Protestant denominations include Anglicans, Methodists, Baptists, Seventh-Day Adventists, and Jehovah's Witnesses, along with other small evangelical groups. Some Gambians also practice traditional indigineous religions (1%). Certain Muslim and Christian holidays are officially observed.