In the early days of the US, the dollar was trusted. The reason it was trusted was that the dollar was backed by physical gold. Those were the days when the dollar was considered “good as gold.” The obvious reason was that a person could take his dollars into any bank, and exchange his dollars for gold.
This changed in 1933 when Americans were forbidden by law to own gold. As far as Americans were concerned, they were now dealing with paper, and could no longer exchange their paper for gold.