How have geographic features in Washington State made it easier for people to settle there? Mountains have served as a highway into the region. Higher elevations in the east have proven to be great for agriculture. Plateaus have allowed new settlements to easily defend themselves. Rivers and coastline have made the region accessible.

Western Lowlands

This is another narrow region about 50 miles wide located between the Coastal region and the Cascade Mountains.  It extends from the Bellingham/Canadian border area to the end of Puget Sound in the Olympia region and south to less populated river valleys of the Chehalis and Cowlitz Rivers.. It is the most densely populated region of the state with Seattle, Everett, and Tacoma as centers of commerce.  It is a hilly area ranging from sea level to 1,000 feet with exposure to salt water on the shores of Puget Sound. Economic growth has been strongest in this region that has been transitioning from lumber and fishing to aerospace related businesses, and computer technology and related commerce.

Cascade Mountains

To the east of the Western Lowlands, running north and south is the Cascade Range.  This range originates in southern British Columbia and stretches through Oregon into Northern California. Mountains in the Cascades average 6,000 feet in height and the range has 5 volcanoes in Washington state: Mt. Baker, Glacier Peak, Mt. Rainier, Mt. Adams, and Mt. St. Helens. The Cascades are a natural barrier between the moist and mild climate of Western Washington and the extreme and very dry Eastern Washington climate.  Sparsely populated, forestry, mining and recreation have been traditional industries in the Cascades.  Because of high amounts of rain and snow in the mountains, the Cascade Range is a major water storage area for the needs of people and industries on both sides of the state.

Columbia Plateau

East of the Cascade Mountains, this is the largest geographical region in the state and it is the world’s second largest lava plateau, second to the Deccan Plateau in India. This huge lava plateau is a result of at least 55 different lava flows 10 to 15 million years ago.  The Columbia River and Snake River both run through the Columbia Plateau providing irrigation water for farming a variety of crops such as wheat, grapes, and potatoes, and fruit trees such as apples and cherries.  Although temperatures fall below freezing in the winter months, summer often brings temperatures to 100 degrees.  It has a semiarid climate that is more extreme than the Coastal and Western Lowland regions. Eastern Washington is more sparsely populated, but there are major population centers: Spokane, the Tri-Cities, Wenatchee, Moses Lake, and Yakima. While agriculture dominates as the main economic driver of the region, manufacturing, high technology, food processing, mining, and recreation are important to the regional economy.  This region has abundant hydroelectric power because of the Grand Coulee Dam and other dams on the Columbia River, and this has attracted manufacturing businesses to the Columbia Plateau.

Rocky Mountains

The Rocky Mountains region is north and east of the Columbia Plateau.  Although the Rocky Mountains range along the west from Canada to the border of Mexico, the Rockies in Washington are a very small segment of this vast mountain range.  The mountains range in altitude from 4,000 to nearly 10,000 feet.  This region is isolated and rugged with long, cold winters and short, cool summers. These mountains also receive less rain than the Olympic and Cascade Mountains, but the rainfall here is higher than the adjacent Columbia Plateau.  Because of these factors, it is sparsely populated. Communities of the region, Omak, Okanogan, and Colville, are supported by lumber, mining and recreation activities.

c it says nothing about connecting those 2 seas.