Over the course of the next few months, the Union arrested thousands of Marylanders suspected of Southern sympathies, including 29 members of the State legislature, a US Congressman representing Maryland, and most of the Baltimore city council.

"Hundreds of Maryland individuals were imprisoned on suspicion of having secessionist sympathies....During the Civil War federal authorities would eventually jail 2,094 Marylanders – including seventeen owners of newspapers, twenty-nine elected members of the state legislature, countless bankers, merchants, and manufacturers – for such political reasons.”

http://www.abrahamlincolnsclassroom.org/Library/newsletter.asp?ID=108&CRLI=156