This island in the Ohio River was the site of Harman Blennerhassett’s plantation; Blennerhassett, a wealthy Anglo-Irish lawyer, was a collaborator in Aaron Burr’s secessionist plot. He had purchased the island in 1798. You can tour the Palladian mansion, grounds, and museum, which has nice archaeological exhibits. Also, the island itself is beautiful, so enjoy the walking trails. Keep your eyes peeled for the ospreys that nest on the island.