The Hundred Islands National Park is located in the City of Alaminos, Pangasinan. The 123 islands (Map of the Hundred Islands National Park) are scattered northward along Lingayen Gulf and cover an area of about 1,860 hectares . They are believed to be about two million years old. Only three of them have been developed for tourists: Governor Island, Quezon Island, and Children's Island. To date, there are only 30 islets that were named with a total area of 970,606.15 square meters (Inventory of Named Islands in the HINP, Location Map of Islands with Names in the HINP)
The islands are actually ancient corals that extend well inland, in an area previously comprising the seabed of an ancient sea. Lowering sea levels have exposed them to the surface and the peculiar "umbrella"-like shapes of some of the islands have been caused by the eroding action of the ocean waves. The Hundred Islands was officially declared a National Park on January 8, 1940 during the time of President Manuel L. Quezon under Presidential Proclamation No. 667 " for the benefit and enjoyment of the people of the Philippines".
Initially under the administration, management and control of the Hundred Islands Conversation and Development Authority (HICDA), this was function passed on to the Philippine Tourism Authority (PTA) by virtue of Presidential Decree No.564 dated March 30, 1982. The Park, plays a very critical role in maintaining biodiversity of the Lingayen Gulf that was established as an Environmentally Critical Area (ECA) and managed as a special Coastal Management Area as per proclamation No.156 dated 25 March 1993 of the then President Fidel V. Ramos.
On June 24,2005, President Gloria Macapagal-Arroyo signed the Executive Order No. 436 transferring the management from the Philippine Tourism Authority to the City of Alaminos. In September 29, 2005, the Philippine Tourism Authority formally turned over the HINP to the City of Alaminos.