Why were homesteads establishes west of the 100th meridian riskier than those established to the east?

in 1878, american geologist and explorer john wesley powell drew an invisible line in the dirt—a long line. it was the 100th meridian west, the longitude he identified as the boundary between the humid eastern united states and the arid western plains. running south to north, the meridian cuts through eastern mexico, texas, oklahoma, kansas, nebraska, the dakotas, and the canadian province of manitoba on its way to the pole.

to meet the requirements if the homesteads

answer; i believe the correct answer is (the willamete valley);

theodore roosevelt 26th u.s. president : i admire his energy and passion. he was a fundamentally good man, brilliantly intelligent, possessed of extraordinary will and ability, supremely self-confident, bold, egalitarian, idealistic…. , lord, can we have him back?