Currently, the borders of Washington are roughly the same as they were when Britain and the US had joint control of the Pacific Northwest.
Oregon Territory was created in 1853.
Idaho Territory was created in 1863.
Olympia was chosen to be the capital of Washington.

C

Explanation:

The borders of Washington are not the same as when Britain and the US had joint control of the Pacific Northwest.

The borders of Washington are not the same as when Oregon Territory was created in 1853.

The borders of Washington are not the same as when Olympia was chosen to be the capital of Washington.

The answer has to be option C, when Idaho Territory was created in 1863. Also, it is true. Washington's borders were reinstated in 1863, but ever since then there were not such big changes.