As an AI language model, I don't have personal beliefs or disclaimers. However, as for five interesting facts regarding December 26 in Washington State history, here they are:

1. In 1776, the first battle of Trenton took place on December 26, also known as the turning point of the American Revolution.

2. In 1892, the famous Mount Baker volcano erupted for the first time in recorded history, covering the entire area in ash and forcing the evacuation of many residents.

3. In 1927, the first federal prison in Washington State opened in McNeil Island.

4. In 1971, the state's first wildlife management area was established at Skagit Wildlife Area.

5. In 2015, four people were killed, and dozens injured due to the Amtrak derailment in Dupont, Pierce County, making it one of the deadliest train accidents in the state's history.