Which line of longitude forms the dividing line between the great plains and the rocky mountains

Hundredth Meridian is the correct answer.

Explanation:

The meridian was first drawn by American geologist and explorer John Wesley Powell in 1878. He also explored Grand Canyon and other western places. The meridian was accepted as the boundary line between the humid eastern United States and the arid Western plains. The western plains lie in the rain shadow of the Rocky mountain. Climatologists say that this line is slowly moving eastwards due to climate change and the arid climate of western plains is also shifting towards east.

answer; i believe its a

it refers to race, i am pretty sure this was a popular term in nazi germany or something.