Assuming your mean Washington state, it would be the Pacific Ocean
The Mississippi river was the border.
The western border of the 13 colonies was formed by the Appalachian Mountains.
The east was bounded by the Mississippi and the West ( andSouth) by the Missouri River.
The Mediterranean sea is located west of Canaan.
The river, Rio Uruguay, borders Uruguay's western border.
The Mississippi river forms the western border of the southern colonies.
The Mississippi river forms the western border of the southern colonies.
The Mississippi River forms Tennessee's western border.
The Great Smoky Mountains form the eastern border with North Carolina.
Colorado River
Andes Mountains.
utah ************************** Note: Arizona's (natural) western border is mostly defined as the Colorado River. (Utah borders to the north!)