In 1997..... Atheist made up 0.209% of the U.S. Prison Population

1997 Federal Bureau of Prisons Statistics
Catholic 29267 39.164%

Protestant 26162 35.008%

Muslim 5435 7.273%

American Indian 2408 3.222%

Nation 1734 2.320%

Rasta 1485 1.987%

Jewish 1325 1.773%

Church of Christ 1303 1.744%

Pentecostal 1093 1.463%

Moorish 1066 1.426%

Buddhist 882 1.180%

Jehovah Witness 665 0.890%

Adventist 621 0.831%

Orthodox 375 0.502%

Mormon 298 0.399%

Scientology 190 0.254%

Atheist 156 0.209%

Hindu 119 0.159%

Santeria 117 0.157%

Sikh 14 0.019%

Bahai 9 0.012%

Krishna 7 0.009%
Denise Golumbaski, Research Analyst, Federal Bureau of Prisons, compiled from up-to-the-day figures on March 5th, 1997