Question: What three states are covered by the volcano range including the North Cascades?

Context paragraphs:
Ecology of the North Cascades: The Ecology of the North Cascades is heavily influenced by the high elevation and rain shadow effects of the mountain range.  The North Cascades is a section of the Cascade Range from the South Fork of the Snoqualmie River in Washington, United States, to the confluence of the Thompson and Fraser Rivers in British Columbia, Canada, where the range is officially called the Cascade Mountains but is usually referred to as the Canadian Cascades.  The North Cascades Ecoregion is a Level III ecoregion in the Commission for Environmental Cooperation's classification system.

North Cascades National Park: North Cascades National Park is a U.S. National Park located in the state of Washington.  The park is the largest of the three National Park Service units that comprise the North Cascades National Park Service Complex.  Several national wilderness areas and British Columbia parkland adjoin the National Park.  The park features rugged mountain peaks and protects portions of the North Cascades range.

Cascade Range: The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California.  It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades.  The small part of the range in British Columbia is referred to as the Canadian Cascades or, locally, as the Cascade Mountains.  The latter term is also sometimes used by Washington residents to refer to the Washington section of the Cascades in addition to North Cascades, the more usual U.S. term, as in North Cascades National Park.  The highest peak in the range is Mount Rainier in Washington at 14411 ft .

Mount Blum: Mount Blum, or Mount Bald, is a 7685 ft summit of the North Cascades range in Washington state, on the western edge of North Cascades National Park.  It is the highest summit of a string of mountain peaks located east of Mount Shuksan and west of the Picket Range.  Two small active glaciers rest on its northern flank.  Mount Blum was named after John Blum, a United States Forest Service fire patrol pilot who crashed nearby in 1931.

Mazama, Washington: is an unincorporated community in Okanogan County (population 200) located in the Methow Valley of Washington, on the east slopes of the North Cascades and North Cascades National Park.  It is located along the North Cascades Highway (Highway 20), 14 mi northwest of Winthrop and about 28 mi south of the Canada–United States border.  Mazama's town center elevation is 2106 ft , and it is located 2.7 mi south of and 4895 ft below Goat Peak.

Mount Redoubt (Washington): Mount Redoubt is a mountain in the North Cascades range in Whatcom County, Washington state.  The peak is located 3.0 mi to the Canada–US border, 16.3 mi east-northeast of Mount Shuksan.  It is the 21st highest peak in the state, with a height of 8956 ft and a prominence of 1649 ft .  Redoubt is in the Skagit Range, a sub-range of the North Cascades, in the Custer-Chilliwack Group which includes Mount Spickard, Mount Redoubt, Mount Custer and Mox Peaks, among others.  Redoubt, Bear, and Depot creeks drain off the mountain, which is composed of Skagit gneiss.  Mount Redoubt is listed as one of the "Classic Eight Peaks" in the North Cascades.

Ross Lake National Recreation Area: Ross Lake National Recreation Area is a US National Recreation Area located in north central Washington just south of the Canada–US border.  It is the most accessible part of the North Cascades National Park Service Complex which also includes North Cascades National Park and Lake Chelan National Recreation Area.  Ross Lake NRA follows the Skagit River corridor from the Canada–US border to the western foothills of the Cascades.  The NRA contains a portion of scenic Washington State Route 20, the North Cascades Highway, and includes three reservoirs: 12,000 acre Ross Lake, 910 acre Diablo Lake, and 210 acre Gorge Lake.  These reservoirs make up the Skagit Hydroelectric Project operated by Seattle City Light.  Nestled in the "American Alps" the Ross Lake NRA bisects the north and south units of North Cascades National Park.  The Shape of the National Recreation area, was designed to prevent the proposed High ross dam from flooding the national park.

Mount Spickard: Mount Spickard (pronounced SPICK' erd) is a 8980 ft mountain peak in the North Cascades, a mountain range in the U.S. state of Washington.  Located just 2 mi south of the Canada–US border, it is part of the Chilliwack Group, a subrange of the Skagit Range which is part of the North Cascades.  It is composed mainly of gneiss and is part of two major drainage basins: that of the Skagit River and Fraser River.

Cascades Volcano Observatory: The David A. Johnston Cascades Volcano Observatory is the volcano observatory that monitors volcanoes in the northern Cascade Range.  Its territory covers Oregon, Washington, and Idaho.  The Cascade range's southernmost reaches extend into Northern California, and Cascade volcanoes south of the Oregon-California border—such as Mt. Shasta—previously fell into CVO's jurisdiction.  However, as of February 2012, these volcanoes fall under the jurisdiction of the newly formed California Volcano Observatory (CalVO), based in Menlo Park, CA which monitors and researches volcanic activity throughout California and Nevada.

Picket Range: The Picket Range is a small, extremely rugged subrange of the North Cascades in the northwestern part of the American state of Washington.  It is entirely contained within North Cascades National Park.  It is about 6 mi long, running northwest-southeast, and lies north of the Skagit River, west of Ross Lake, and east of Mounts Baker and Shuksan.  There are at least 21 peaks in the range over 7500 ft high.

Supporting paragraphs: Cascades Volcano Observatory Cascade Range
Answer: Oregon, Washington, and Idaho