Analyze the map, then answer the question that follows.

A map titled 2010 Census Results - United States and Puerto Rico. It shows a key of People per Square Mile by color. Yellow is 0.0 to 0.9. Light green is 1.0 to 19.9. Green is 20.0 to 88.3. Teal is 88.4 to 499.9. Blue is 500.0 to 1,999.9. Dark blue is 2,000.0 to 69,468.4. The western half of the United States are mainly light green and green with some areas yellow and teal. The eastern half of the United States are mainly teal and blue. Areas of dark blue increase in the North.

According to this map, which region of the United States has the highest population density?

The Pacific Northwest
The Southwest
The Rocky Mountain region
The Northeast
The Midwest