Whenever you read about the American Civil War the majority of information is focused on the the East Coast as that's where the majority of slavery took place and the majority of battles were fought. But what were the West Coast states doing during this time?
They were certainly not inactive. While the most well-known military action west of what is termed the "western theater" of the civil war is probably the battle of Glorietta Pass, which is usually brought up when discussing the relative calmness of the west coast during the conflict, there were secessionist groups in southern California and both it and Oregon sent troops to fight for the union. Fun fact- in 1864, Irwin McDowell, (in)famous for Bull Run, took over the department of the Pacific in 1864, a post which somewhat helped him to repair his reputation, though not by much.
The secessionist movement in California was rather rapidly contained, both by simply not receiving Confederate aid and funds it was supposed to receive, and Union troops being aware of the danger and moving down in an effort to permanently secure the state for the Union, which was ultimately successful at Belleville and San Bernardino without much bloodshed. As the war dragged on, Californian volunteers were called up to replace the regulars already sent east, and some Californians went east to enlist. On account of California sending gold to aid the Union war effort, Californians fought against local secessionist raids on the shipments, as well as the Navy engaging pirates along the coast. Those troops sent against the Confederate attempts in New Mexico were also sent against natives during the war.
Oregon also mustered volunteers and sent career soldiers east, which were supposed to be replaced by volunteers from other states, against which there was some resentment, though no secessionist groups like in California formed. In 1862, Oregon raised the 1st Oregon volunteer cavalry, and in 1864, a volunteer infantry as well. Those mainly skirmished with natives, as did the other guard regiments formed after then. Notably, an Oregon Senator died at Balls Bluff serving with the "California Regiment", the 71st Pennsylvania Infantry.
Washington, then. It's not yet a state, as is Idaho. The territory did raise volunteers as well, though, who served protecting lines of communication in the department's north and also appear to have fought natives during the war (a common theme); though I'd definitely need to research more than I can provide at the drop of a hat right now. Obviously, details of the remote areas are harder to find.