The censuses of prisoners associated with the U.S. censuses from 1900 to 1930 reported only sentenced prisoners. Article 1, Section 2, and Amendment 14 of the U.S. Constitution requires that the census count all persons. According to the instructions to enumerators (see, e.g. 1910), all prisoners, including unsentenced prisoners, were to be counted. Nonetheless, census reports on prisoners reported only sentenced prisoners. Unsentenced prisoners apparently were included in the over-all census population total.

Census officials obscured not reporting on unsentenced prisoners. The introduction to the census of prisoners in 1904 (the prisoner census associated with the national census of 1900) observed:

The reason for not classifying persons awaiting trial or held as witnesses, or the insane, or other similar groups , with sentenced prisoners are perhaps too obvious to require explanation.

Persons awaiting trial account for a third or more of prisoners held in local jails. Such prisoners were reported with sentenced prisoners before 1900, and after 1930. The reason for not reporting such prisoners in the census report on prisoners in 1904 is far from obvious. Census officials provided no explanation for that change in reporting.

Subsequent reporting of the legal status of prisoners has been far from clear. Persons held in prison without a prison sentence have not been convicted of any crime. Official statistics seem to downplay the importance of unsentenced incarceration.