The Washington Territory was established in 1853, and it initially included what would become both Washington and Idaho. The Pig War, a standoff between the United States and Great Britain over the San Juan Islands, occurred from 1859 to 1872.
Idaho became a separate territory on March 4, 1863, after the split from the original Washington Territory. Therefore, the split into Idaho and Washington territories occurred after the Pig War had begun but before it officially ended.