Huffington Post says:
Prisons would also become major centers for Islamic outreach. Today, prison officials, prison chaplains and scholars claim that Islam is the fastest growing religion behind bars. Although there are no reliable statistics, estimates suggest that 35,000-40,000 inmates convert to Islam each year, and nationwide, it is estimated that 15 percent of the U.S. prison population is Muslim, or as much as 350,000 current Muslim inmates.
When I searched for the stats, I came across the Wikipedia page about Islam in the United States which says:
In addition to immigration, the state, federal and local prisons of the United States may be a contributor to the growth of Islam in the country. J. Michael Waller claims that Muslim inmates comprise 17–20% of the prison population, or roughly 350,000 inmates in 2003. Waller states that these inmates mostly come into prison as non-Muslims. He also claims that 80% of the prisoners who "find faith" while in prison convert to Islam.
The source cited for the above claim is either dead or not accessible due to some unknown reason. (shows me a white blank page)
Is 15 percent of the U.S. prison population Muslim? Is J. Michael Waller's claim reliable?