When I was researching my Cassidy family from Mullacrew Louth I found an obituary in the Dundalk Democrat May 6th 1906 for Hugh Cassidy (not a direct line) which described him as ‘one of the most stalwart Nationalists in the County Louth, and who, from the days when he was imprisoned as a Forster suspect down to the days when he stood for Independent Opposition in the Nineties, never faltered from what he thought his duty as an Irishman to his country’.
I have not found any other info relating to his imprisonment so I am not sure if it was in Dundalk prison. I assume it was in connection with Land League activities. I would be interested to know if anyone had any further information.