 Biographer and historian William J. Cooper notes that Adams "does not loom large in the American imagination", but that he has received more public attention since the late 20th century due to his anti-slavery stances.Cooper writes that Adams was the first "major public figure" to publicly question whether the United States could remain united so long as the institution of slavery persisted.Historian Daniel Walker Howe writes that Adams's "intellectual ability and courage were above reproach, and his wisdom in perceiving the national interest has stood the test of time."