Which nations claimed land west of the Rockies?

Originally Spain, Great Britain, Russia, and the United States claimed the territory.

Explanation:

The Oregon Territory stretched from the Pacific coast to the Rocky Mountains, encompassing the area including present-day Oregon, Washington, and most of British Columbia.

Spain, Great Britain, Russia and The United States

Explanation:

albany plan of union, 1754. the albany plan of union was a plan to place the british north american colonies under a more centralized government