The Congressional Research Service sets out the facts, and the ACLU concludes that
From 1980 to 2012, the federal prison population has ballooned from 25,000 to 219,000, a 790% increase.
Population has increased by approximately 6,100 inmates each year since 1980. In the 50 years before that, the population increased by 12,000 total.
From 2000 to 2011, appropriations for the Bureau of Prisons increased by more than $2.7 billion.