People searching for someone in custody often search the wrong system for days. The distinction is simple once you know it.
County jail
Jails are operated by county sheriffs or county corrections departments. They hold people awaiting a first appearance, awaiting trial, serving short sentences (commonly under a year, though the line varies by state), held on holds for other agencies, and awaiting transfer. Populations turn over rapidly — a county jail roster can change substantially within a day.
Each county publishes its own roster, in its own format, on its own schedule. That fragmentation is why directories like this one exist.
State prison
State departments of corrections hold people serving longer sentences after conviction. They operate a single statewide offender search covering all facilities in that state, and their records are stable — someone may be listed for years rather than days.
Federal custody
People charged with federal offences are held by the U.S. Marshals Service, frequently in contracted county jails, and after sentencing by the Federal Bureau of Prisons. Federal detainees may appear on a county roster with a federal agency listed as the holding authority, or may not appear publicly at all.
Why someone disappears from a county roster
Release is the obvious explanation, but it is not the only one. Transfer to state custody after sentencing removes them from the county system. Transfer to another county on a hold does the same. Transfer to a hospital or a mental-health facility can remove a listing. Some facilities also remove entries immediately at release while others lag by hours.
If someone vanishes without an expected release, check the state corrections search first, then neighbouring counties.
Which system to search, in order
Start with the county where the arrest occurred. If the person was recently sentenced, search the state department of corrections. If the charges are federal, use the federal inmate locator. If an immigration hold is involved, the relevant federal detainee locator is a separate system again.
Why the data quality differs
State systems are centralised, funded and maintained, so their records are comparatively clean. County jail systems range from modern portals with structured data to pages that have barely changed in twenty years. This directory normalises what counties publish, but it cannot improve the underlying record — if a county publishes only names and booking dates, that is all there is.