The handy CPI calculator at FRB Minneapolis came to the rescue: $1 in 1925 is $13.67 in 2015. That is, you'd need $13.67 million in 2015 to have the purchasing power of someone with $1 million in 1925!
If you want to dig a little deeper, the Fed's full annual CPI data 1801-2015 appear in the table below (year, CPI price level, inflation rate). Note that the price level was stable during 1801-1913, after which it grew steadily forevermore. Quiz: Besides steady inflation, what didn't exist in the U.S. before 1913 but has been with us ever since? You know the answer.
Don't get me wrong. I'm not wishing we were back in 1880 with no Federal Reserve System. But the price level pattern certainly does suggest that the benefits delivered by central banks, printing fiat money, come at a significant cost -- the inflation tax -- which is highly regressive, borne disproportionately by the unsophisticated poor.