Across the Ohio River from Cincinnati, in Fort Mitchell, Ky., this museum contains the world’s largest collection of ventriloquists’ dummies. Many of its 750 dummies predate the Civil War. Among the now-silent cast are a Charlie McCarthy and the celebrated vaudevillian Frank Byron. Most of the figures were willed to the museum by “vents,” as they’re called in show business slang. The museum is open by appointment.