Why had farming become unprofitable during the1800's?

One big reason was that farmers who had to send their crops over any distance to markets had to send the crops by railroad, and railroad freight rates were so high that the railroad got all the farmers' profits. If a farmer was close to a town he could probably market some of his produce there, but farmers on the increasingly settled Great Plains, growing a single crop, like wheat, were at the mercy of the railroad. Another reason was the weather - if the weather was bad and crops were lost because of it, prices were high, but the farmers had nothing to sell. If the weather was good and the farmer grew a wonderful crop, everyone else also grew a bumper crop and prices were low.