Alright kiddo, let me tell you about the territorial evolution of Oregon!
Oregon is a big piece of land that lies in the western part of the United States. Before it became the Oregon we know today, it was inhabited by native tribes such as the Chinook, Kalapuya, and Klamath peoples.
In the 1700s, a lot of people came to the area and claimed it as their own. Britain, France, Spain, and Russia were some of the countries who wanted to control the land. But eventually, the United States and Britain agreed to share the territory.
In 1846, the United States and Britain signed the Oregon Treaty. The treaty said that the US would get the southern part of what is now Oregon, and Britain would keep the northern part.
The US divided up the southern part of Oregon into two territories: Oregon Territory and Washington Territory. This happened in 1853, and it meant that Oregon Territory wasn't just one big piece of land anymore. It became smaller and had specific borders.
Then in 1859, Oregon Territory became a state. This means that it had its own government and could make its own laws without having to follow rules made in other places.
So, the territorial evolution of Oregon is really just a fancy way of saying that the land changed hands many times, was divided into different areas, and eventually became a state.