Complex sentence: The White Mountains are a mountain range that covers about a quarter of the state of New Hampshire and a small portion of western Maine in the United States, and are considered the most rugged mountains in New England and also the Appalachian Mountains.
Split into simpler sentences: The White Mountains is a geographical region named for a mountain range that covers about a quarter of the state of New Hampshire and a small portion of western Maine in the United States. They are considered the most rugged mountains in New England and are part of the Appalachian Mountains.