Expansionists thought the U. S. should go to war with Spain mainly because A. It would help American business.

B. They had a deep desire to see the Cuban people freed.

C. They were afraid Spain might attack the U. S. and take its property.

D. They thought the U. S. should look for new land.

C. they were afraid Spain might attack the U.S and take its property

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