Quoted from http://useconomy.about.com/od/commoditiesmarketfaq/a/Gold-Price-History.htm
"The United States used the British gold standard until 1791, when it set the price of gold at $19.49. In 1834, it raised it to $20.69, then lowered it slightly to $20.67 in 1837. There it remained until 1934, when the Gold Price Act was signed. It prohibited private ownership of gold in the U.S., and allowed President Roosevelt to raise the price of gold to $35 an ounce."
(Source: Lawrence H. Officer and Samuel H. Williamson, Measuring Worth, The Price of Gold, 1257-Present, 2013; FEE.org, Gold Policy in the 1930s)
Current gold prices: