How was sharecropping a trap

During Reconstruction, former slaves--and many small white farmers--became trapped in a new system of economic exploitation known as sharecropping. Lacking capital and land of their own, former slaves were forced to work for large landowners.

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain