People stop using the Santa Fe trail for shipping when

D the railroad ended shipments by caravan

Answer D.

Explanation:

This is because when the Railroad came to New Mexico it became a better and more efficient way of shipping, Therefore making the answer to the question option "D"

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.