Gold was slowly becoming more valuable in terms of silver and the legal ratio of 15 to 1 in the United States (at which both metals were admitted free to the mint) proved to have undervalued gold.

Gold largely left circulation and silver and bank notes formed the greater part of our circulating medium.

Then, in 1834, soon after the production of gold had begun to increase somewhat more rapidly than that of silver, the legal ratio of the United States was changed to 16 to 1.

This brought a good deal of gold back into circulation and gradually drove out most of the silver (the heavier coins disappearing first).
In the decade 1841-50 the average annual value of the gold production had, for the first time since the early sixteenth century, exceeded that of silver.

Then, from 1848 to 1850, came the great gold discoveries in California and in Australia.