Provincial Boundaries

 Ilocos Sur is located along the western coast of  Northern Luzon. It is bordered by Ilocos Norte to the  north, Abra to the northeast, Mountain Province to  the east, Benguet to the southeast, La Union to the  south, and the China Sea to the west. Its area of  2,579.58 square kilometers occupies about 20.11%  of the total land area of Region 1.

 >The topography of Ilocos Sur is undulating to rolling  with elevations ranging from 10 to 1,700 metres (33  to 5,600 ft) above sea level.

http://upload.wikimedia.org/wikipedia/commons/d/d5/Ph_locator_map_ilocos_sur.png