Question: Pinkham Notch has walls formed by one of the mountains in which New Hampshire county?

Context paragraphs:
Evans Notch: Evans Notch (elev.  1410 ft ) is a mountain pass located in the White Mountains in Maine, United States, about 1 mi east of the New Hampshire border.  It is the easternmost notch through the White Mountains (the next ones to the west being Carter Notch and Pinkham Notch).  To the south, the notch is drained by the Cold River, which leads via the Charles River to the Saco River, which in turn flows into the Gulf of Maine east of Saco and Biddeford.  The Mad River is a small mountain stream that joins the Cold River from the west about 2 mi south of the height of land, after dropping over Mad River Falls.  The notch is drained to the north by Evans Brook, a tributary of the Wild River, which flows north to the Androscoggin River.  The Androscoggin leads east and south to the Kennebec River at Merrymeeting Bay north of Bath, Maine.

Wildcat Mountain (New Hampshire): Wildcat Mountain is a mountain located in Coos County, northern New Hampshire, United States.  The mountain is part of the Carter-Moriah Range of the White Mountains, on the east side of Pinkham Notch.  Wildcat Mountain faces Carter Dome across Carter Notch to the northeast, and Mount Washington across Pinkham Notch to the west.

Pinkham Notch: Pinkham Notch (elevation 2032 ft. / 619 m) is a mountain pass in the White Mountains of north-central New Hampshire, United States.  The notch is a result of extensive erosion by the Laurentide ice sheet during the Wisconsinian ice age.  Pinkham Notch was eroded into a glacial U-shaped valley whose walls are formed by the Presidential, Wildcat, and Carter-Moriah ranges.  Due to the volatility of the area's climate and rugged character of the terrain, a number of rare or endemic ecosystems have developed throughout the notch.

Middle Moriah Mountain: Middle Moriah Mountain is a mountain located in Coos County, New Hampshire.  The mountain is part of the Carter-Moriah Range of the White Mountains, which runs along the northern east side of Pinkham Notch.  Middle Moriah is flanked to the northeast by Shelburne Moriah Mountain, and to the southwest by Mount Moriah.

Mount Washington Auto Road: The Mount Washington Auto Road — originally the Mount Washington Carriage Road — is a 7.6 mi toll road that extends from New Hampshire Route 16 in Green's Grant, just north of Pinkham Notch, westward across Pinkham's Grant and Thompson and Meserve's Purchase to the summit of Mount Washington in the White Mountains of the US state of New Hampshire.  The road climbs 4618 ft from an altitude of 1527 ft at the bottom to 6145 ft at the top, an average gradient of 11.6%.  The road was completed and opened to the public in 1861.

Mount Moriah (New Hampshire): Mount Moriah is a mountain located in Coos County, New Hampshire.  The mountain is part of the Carter-Moriah Range of the White Mountains, which runs along the northern east side of Pinkham Notch.  The summit is approximately 5 mi southeast of the center of the town of Gorham.  Mount Moriah is flanked to the northeast by Middle Moriah Mountain and to the southwest by Imp Mountain.

Kinsman Notch: Kinsman Notch (elev.  1870 ft ) is a mountain pass located in the White Mountains of New Hampshire, United States.  It is the westernmost of the major notches through the White Mountains (the others being Franconia Notch, Crawford Notch, and Pinkham Notch).  To the southeast, the valley of the notch is drained by the Lost River, leading to the Pemigewasset River, and ultimately the Merrimack, flowing into the Gulf of Maine.  The northwest half of the notch is drained by Beaver Brook and the Wild Ammonoosuc River, part of the Connecticut River watershed leading to Long Island Sound.

Shelburne Moriah Mountain: Shelburne Moriah Mountain is a mountain located in Coos County, New Hampshire.  The mountain is part of the Carter-Moriah Range of the White Mountains, which runs along the northern east side of Pinkham Notch.  Shelburne Moriah is flanked to the southwest by Middle Moriah Mountain.  It is the northernmost Moriah Range summit along the Appalachian Trail, which crosses the Androscoggin River at Shelburne, New Hampshire, and continues north into the Mahoosuc Range.

Carter Dome: Carter Dome, or simply The Dome, is a mountain located in Coos County, New Hampshire.  The mountain is part of the Carter-Moriah Range of the White Mountains, which runs along the northern east side of Pinkham Notch.  Carter Dome is flanked to the northeast by Mount Hight and to the southwest by Wildcat Mountain (across Carter Notch).

Carter-Moriah Range: The Carter-Moriah Range of mountains is located in the White Mountains, in Coos County, New Hampshire.  The range forms the northern east side of Pinkham Notch, opposite the northern Presidential Range.  The range is also referred to as the Carter Range.

Supporting paragraphs: Pinkham Notch Wildcat Mountain (New Hampshire)
Answer: Coos County