The Highlands of Connecticut, New Jersey, New York, and Pennsylvania is a multi-state region in the northeastern United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It is defined by its geological features and characterized by the largely undeveloped foothills

Foothills

Foothills are geographically defined as gradual increases in elevation at the base of a mountain range. They are a transition zone between plains and low relief hills to the adjacent topographically high mountains.-Examples:...

 that form the edge of the New York-New Jersey-Connecticut Tri-State Region. Formally established by the U.S. Congress in 2004, the Highlands encompass some of the last major corridors of undeveloped land along the Eastern Seaboard

Eastern seaboard

An Eastern seaboard can mean any easternmost part of a continent, or its countries, states and/or cities.Eastern seaboard may also refer to:* East Coast of Australia* East Coast of the United States* Eastern Seaboard of Thailand-See also:...

, and form a regional greenbelt that provides critical ecological services to the most densely populated part of the United States.