The factor that had a major impact on the movement of people from the east to the west in the late 1800s is:
B. the Louisiana Purchase
The Louisiana Purchase, made in 1803, significantly expanded U.S. territory westward and set the stage for westward expansion. Although it occurred earlier than the late 1800s, it influenced the movement of people to settle and develop the lands acquired. The other options (the 14th Amendment, restrictions on immigration, and the creation of Indian Reservations) played roles in different contexts and might not directly relate to the westward migration in the same way.