|Maryland lies in the Mid Atlantic region of the US in an area of about twelve thousand square miles. The population of the state, as estimated in 2008, stands at more than 5.6 million. Moreover, according to a survey conducted by the U.S. Census Bureau in 2007, the median household income of Maryland was found to be the highest among all states of the nation. The state is bordered by Delaware to the east, Pennsylvania to the north and Virginia, West Virginia and the District of Columbia to the west and south. Its topographical features include sandy dunes in the east, low marshlands near the bay, pine groves in the western mountains and rolling hills of oak forest in the Piedmont region. The tallest mountain in state is Hove Crest, which has a height of 3,360 feet, while sea level at Atlantic Ocean is its lowest area. It joined the Union in 1788 and became the seventh state to ratify the US Constitution. Maryland has a number of biotechnology firms, educational institutions and research agencies including John Hopkins University, the National Institutes of Health and the National Institute of Standards and Technology. Maryland is popularly known as the Old Line State and the Free State. The largest city is Baltimore and the capital is Annapolis.