Which of the Following Statements Is Most Accurate

Which of the following statements is most accurate?

A) In 1990, more than half of the population of the United States lived west of the Great Plains.
B) By 1990, more than half of the population of the United States lived west of the Rocky Mountains.
C) By 1990, more than half of the population of the United States lived west of the Grand Canyon.
D) By 1990, more than half of the population of the United States lived west of the Mississippi River.
E) By 1990, more than half of the population of the United States lived west of the Colorado River.