Which of the following statements is TRUE?
◦ By 1990, more than half of the population of the United States lived west of the Colorado River.
◦ By 1990, more than half of the population of the United States lived west of the Rocky Mountains.
◦ In 1990, more than half of the population of the United States lived west of the Great Plains.
◦ By 1990, more than half of the population of the United States lived west of the Mississippi River.
◦ By 1990, more than half of the population of the United States lived west of the Grand Canyon.