Final answer:
Vermont is the state that has the Green Mountains on its border with Massachusetts. These mountains are part of the rugged terrain that characterizes northern New England compared to the more populous southern states.
Step-by-step explanation:
The state with the Green Mountains on the border with Massachusetts is Vermont. This mountain range is part of the Appalachian Mountains and extends southward from Quebec in Canada into the state of Vermont, providing a natural border between Vermont and Massachusetts in some areas. For a visual, imagine the profile of Great Blue Hill in Milton, MA, which represents the kind of terrain transitions experienced as one moves toward the Green Mountains. As one heads north from Boston, the landscape changes, and the rolling hills transition into more rugged terrain, indicative of northern New England's distinctive geographical features like the Green Mountains.
States like Vermont, New Hampshire, and Maine are significantly less populated than their southern New England counterparts due to rugged terrain and less fertile soil. For example, Maine is extensively forested, with a vast expanse of its territory covered in forests and possessing large areas with no permanent human inhabitants. Vermont, while being more populous than Maine, also boasts significant forested areas and a focus on outdoor recreation and tourism, particularly around its famed Green Mountains.