In 1797, Harman Blennerhassett and his wife moved to Marietta, Ohio, where they purchased 174 acres of land on an island in the Ohio River. The land formerly belonged to George Washington. The island is located near Belpre. The Blennerhassetts intended to make the island their home.
For the first several years that the Blennerhassetts lived on the island, they resided in a blockhouse. In 1800, they moved into a mansion. In their new home, the couple lived the life of the wealthy. Harman conducted scientific experiments, formed an extensive private library, and paid detailed attention to his agricultural fields. The couple became well known for their hospitality, and many travelers down the Ohio River stopped at the Blennerhassett home. The couple's most famous guest was Aaron Burr, a former Vice President of the United States.
In 1805 and 1806, the Blennerhassetts assisted Burr in his scheme to break away the western part of the United States to form a new country that he would lead. The United States government heard rumors of the uprising and sent a detachment of Virginia militia to seize the Blennerhassetts' island. Harman Blennerhassett was in hiding. His wife was away in Marietta. When she returned, she discovered that the militiamen had ransacked the home. She fled with her three children. Her husband was arrested a few weeks later, but he quickly gained his release. The Blennerhassetts briefly returned to their mansion, but now destitute from Harman's support of Burr, they sought their fortunes in Mississippi. The Blennerhassetts' former home, now under new ownership, burned in 1811. During the 1980s, the mansion was reconstructed on its original foundations. The island is now a West Virginia state park.