throughout the life of the institution as a prison/hospital, approximately two-thirds of those sent to the u.s. public health service hospital were considered volunteers. while many traveled to the institution on their own to volunteer for treatment, other so-called volunteers were in fact motivated to go there in lieu of federal sentencing. the remaining one-third of the prison's population, which reached 1,499 inmates at its peak, were there due to federal charges either directly or indirectly related to drug use.