Which technology settlers establish farms on the great plains

answer:

repeating rifle, wooden sluices, electric light bulb. sod houses, sheep shearers, wool carders. telegraph, railroad, creation of yellowstone national park. steel plow, windmill, barbed wire, reaper.

explanation:

the only true answer is that it expanded after 325 ad.

nothing certain is known about what happened, but it seems that the country declined gradually, perhaps due to bad government, or, more likely, due to a series of bad harvests, which resulted in widespread and recurrent famine.