The map shows population density in the United States. Population distribution often relates to an area’s environment and physical features. The population distribution shown on the map suggests there might be

less helpful physical features in New Mexico in the Southwest and New York in the Northeast.
more helpful physical features in Florida in the Southeast and North Dakota in the Midwest.
less helpful physical features in Pennsylvania in the Northeast and Idaho in the Northwest.
more helpful physical features in Massachusetts in the Northeast and Virginia in the Southeast.