“The United States consists of 11,078,300 Census Blocks,” Freeman explained on his Tumblr. “Of them, 4,871,270 blocks totaling 4.61 million square kilometers were reported to have no population living inside them. Despite having a population of more than 310 million people, 47% of the USA remains unoccupied.”

Most of the green shading highlights areas where human habitation is either restrictive (lakes, rivers, floodplains, mountains, etc) or prohibited by social or legal convention (wilderness protected states, recreational areas such as state parks, and more).