St. William Cathedral, also known as Laoag Cathedral, was originally built in 1612 by Augustinian friars to replace a wooden chapel. It is known for its Italian Renaissance design and its Sinking Bell Tower, which sinks into the ground at a rate of an inch a year.

Laoag (Ilocano for 'light or clarity'), is an old, flourishing settlement known to Chinese and Japanese traders when the Spanish conquistador Juan de Salcedo arrived at the northern banks of Padsan River in 1572. Augustinian missionaries established the Roman Catholic Church in the area in 1580 and designated Saint William, the Hermit as its patron saint.