From Longman Dictionary of Contemporary Englishwesternmostwest‧ern‧most /ˈwestənməʊst $ -tərnmoʊst/ adjective SGDNfurthest west the westernmost tip of the island
Examples from the Corpus
westernmost• Its expressed aim was to regain control of the westernmost 14 miles of border below Imperial Beach and San Ysidro.• the westernmost island of South America• Wreckage in the vicinity of the break point fell first and was recovered in the westernmost of three major debris fields.• This westernmost part of the Soviet Union used to draw little attention, except from spies.• Atchison lies at the westernmost point in this bend, on the western side of the river. 