Ever since the New York Stock Exchange began in 1792,  the United States has had a stock market. Early stockbrokers looked to Europe for a model to build their system on and decided to base it on the system of Spain. This was largely due to the fact that the U.S. dollar's value had been based on the value of the Spanish real. The real was the Spanish silver dollar and was divided into eight parts. This evolved from the method of counting on the hands, similar to the decimal system. The difference was that the decimal system used the thumbs as part of the number while this other system used the thumbs to denote the total of the four fingers. Therefore, a person would count to four on one hand and then use the thumb to indicate a total while they counted on the other hand. Two thumbs equaled eight. The real could be broken into two, four or eight parts, giving birth to the term pieces of eight.  So when the U.S. stock market began, they based the stock values on one-eighth fractions.