In 1900, the US Govt enacted the the Gold Standard Act, which made gold the sole standard for all currency (up until 1971). Prior to that act, both gold and silver had been used.
The populist free silver movement in the late 1800s had been undertaken by westerners to promote unlimited silver coinage to benefit the common man. Perhaps the Wizard of Oz novel (written in 1900) is some insight by Baum into the foolishness/greed of the Roths/Illums and the consolidation of power that did, in fact, happen. Dorothy's shoes were silver shoes, after all.