What is the name of plain that stretches across the middle of the US?

Answer 1

The area is called the Great Plains. It incorporates the westernmost portion of the North American Interior Plains, which extend east to the Appalachian Plateau. States and provinces which include some portion of the Great Plains are:

• Texas
• New Mexico
• Oklahoma
• Colorado
• Kansas
• Wyoming
• South Dakota
• North Dakota
• Montana
• Alberta, Canada
• Saskatchewan, Canada
• Manitoba, Canada
  

The United States Geological Survey divides the Great Plains into ten subdivisions:

1. Missouri Plateau, glaciated - east-central South Dakota, northern and eastern North Dakota and northeastern Montana
2. Missouri Plateau, unglaciated - western South Dakota, northeastern Wyoming, southwestern South Dakota and southeastern Montana
3. Black Hills - western South Dakota
4. High Plains - eastern New Mexico, northwestern Texas, western Oklahoma, eastern Colorado, western Kansas, most of Nebraska (including the Sand Hills) and southeastern Wyoming
5. Plains Border - central Kansas and northern Oklahoma (including the Flint, Red and Smoky Hills)
6. Colorado Piedmont - eastern Colorado
7. Raton section - northeastern New Mexico
8. Pecos Valley - eastern New Mexico
9. Edwards Plateau - south-central Texas
10. Central Texas section - central Texas

The region is about 500 miles (800 km) east to west and 2,000 miles (3,200 km) north to south and covers an area of approximately 1,300,000 square km.