Dartmoor Prison, a British prison in Prince Town, Devonshire. It is near the wild, elevated Dartmoor plateau. The prison was built for French prisoners during the Napoleonic Wars. Later, during the War of 1812, it was used for United States captives. On April 6, 1815, seven Americans were killed in an attempt to escape; this incident is known as the Dartmoor massacre. Since 1850 the prison has been used for convicts.