Williamette Valley

Willamette Valley
Farmscape in northern Polk County
Country	United States
State	Oregon
Borders on	Cascade Range (East) Oregon Coast Range (West) Calapooya Mountains (South)
Side valleys
- left	Tualatin Valley
River	Willamette River
Population	2.9 million
Geology	alluvial plain
Orogeny	Catastrophic ice-age flooding
Period	several
The Willamette Valley contains most of Oregon's population; it extends from Portland in the north to Eugene in the south.

The Willamette Valley (/wᵻˈlæmᵻt/) is a 150-mile (240 km) long valley in the Pacific Northwest region of the United States. The Willamette River flows the entire length of the valley, and it is surrounded by mountains on three sides – the Cascade Range to the east, the Oregon Coast Range to the west, and the Calapooya Mountains to the south. It forms the cultural and political heart of Oregon, and is home to approximately 70 percent of its population including its three largest cities: Portland, Eugene and Salem, the state capital.

The valley's numerous waterways, particularly the Willamette River, are vital to the economy of Oregon, as they continuously deposit highly fertile alluvial soils across its broad, flat plain. A massively productive agricultural area, the valley was widely publicized in the 1820s as a 'promised land of flowing milk and honey'. Throughout the 19th century it was the destination of choice for the oxen-drawn wagon trains of emigrants who made the perilous journey along the Oregon Trail.

Today the valley is often considered synonymous with "Oregon Wine Country", as it contains more than 19,000 acres (7,700 ha) of vineyards and 500+ wineries.

Much of the Willamette’s fertility is derived from a series of massive ice-age floods that came from Lake Missoula in Montana and scoured across Eastern Washington, sweeping its topsoil down the Columbia River Gorge. When floodwaters met log- and ice-jams at Kalama in southwest Washington, the water caused a backup that filled the entire Willamette Valley to a depth of 300 to 400 feet (91 to 122 m) above current sea level. Some geologists suggest that the Willamette Valley flooded in this manner multiple times during the last ice age. If floodwaters of that magnitude covered Portland (elevation 20 feet (6.1 m)) in 2010, only the tops of the West Hills, Mount Tabor, Rocky Butte, Kelley Butte and Mount Scott would be visible, as would only some of the city’s tallest skyscrapers. Elevations for other cities in the valley are Newberg, 175 feet (53 m); Oregon City, 138 feet (42 m); McMinnville, 157 feet (48 m); Salem, 154 feet (47 m); Corvallis, 235 feet (72 m); and Eugene, 430 feet (130 m). The lake gradually drained away, leaving layered sedimentary soils on the valley floor to a height of about 180 to 200 feet (55 to 61 m) above current sea level throughout the Tualatin, Yamhill and Willamette valleys.