The first known European observation of Whidbey Island was during the Spanish expedition of Manuel Quimper and Gonzalo López de Haro at the `` Princesa Real '' in 1790 . The first known European sighting of Whidbey Island was during the 1790 Spanish expedition of Manuel Quimper and Gonzalo López de Haro on the `` Princesa Real '' . The first known Spanish sighting of Whidbey Island was during the 1790 European expedition of Manuel Quimper and Gonzalo López de Haro on the `` Princesa Real '' .