The Parish of San Diego de Alcala was established in 1582 in its present site and was transferred to Silangan in the island of Alabat in 1638. It was burned by Dutch invaders in 1665 and reconstructed at its present site in 1846. It is bounded at the southeast by the municipality of Lopez, at the south by the sea, and at the northeast by the municipality of Plaridel, formerly a barrio of Atimonan. The first parish priest was either Fray Diego De Oropesa or Fray Esteban Ortiz of the Franciscan order.