That awkward distinction goes to Washington state. In the mid 1800’s the territory of Washington was considerably larger than the current state we recognize. Oregon had just achieved statehood and established north and east borders that helped define Washington territory into something that looked like the solid lines below:
But in 1860, gold was discovered in the mountains in the eastern part of Washington territory. Instead of seeing it as a fortuitous windfall that would enrich the entire region, the territorial government feared the worst. Just two years before, gold had been discovered in Colorado and almost immediately 50,000 people descended upon the area. The influx brought a level of lawlessness that the territorial government of Colorado found extremely difficult to control.
And worrying about the lawlessness of tens of thousands of miners was only part of the problem for the territory of Washington. Governing a wide area separated by mountains was a task in itself, but the cultural makeup of the type of people flooding the mountain areas was quite different from the settlers who were already in the region, based primarily near Puget Sound. Fearing that the large numbers of newcomers would soon have a political voice that could change the cultural landscape of the soon-to-be-state, lawmakers made the decision to divide the territory and cut off those “problem” mountains.
The region they spun-off was later divided between Idaho and Montana.