When early settlers began to move north, they moved north of the 49th parallel. Puget Sound. Seattle. the Columbia River.

The 49th parallel is a circle of latitude that crosses the Northern Part of the country, it is relevant because it represent the border with Canada.

Puget Sound is the name of an entire territory that was inhabited by settlers in this part of the coutry after a series of historical events.

Seattle is the name of an specific settlement in this area that then become a big city.

As settlers continued moving north for different reasons, for example, more newcomers, they needed more land. Pioneers continued exploring the territory north of the Columbia River. This is the correct answer