How did the US devalue the dollar during the US Civil War?

The US Civil War was a costly operation for the US. It had to raise funds through many ways. Increasing taxes, and selling bonds for example. Another way to pay for its expenses was to begin printing money. During the course of the war it simply printed $150 million to pay its expenses. This devalued the dollar, but in wartime all avenues of raising money must be found. The easiest way was to pay expenses by simply creating money.