There are typically said to be three stages of development of a frontier in the context of the United States. These three stages are trade, settlement, and statehood. Oregon went through all three of these stages.
The first whites to spend significant amounts of time in the Oregon Territory were traders. As an example of this, the British built Fort Vancouver in what is now Washington State in 1824. This was to serve as a place to collect furs that were brought to the British by Native Americans. The fur trade dominated contacts between whites and Natives for some time.
However, the Oregon country soon came to attract many migrants from the East. The heyday of the Oregon Trail started in the 1840s. During this time, huge numbers of settlers came out to live in Oregon. The numbers in which these people came made it so that they could not possibly have good relations with the Indians. This led to a situation where there was more conflict between the two.
Finally, Oregon moved towards statehood. In 1846, the US took official control of the southern part of the Oregon Territory. Oregon was organized as a territory in 1848 and became a state in 1859.