If someone is attempting to locate an inmate within the penal system, then he or she should use an inmate locator of some sort, depending upon exactly what penal system the inmate might be in. If the searcher is attempting to find an inmate who is in the Federal penal system, then he or she should use the FBOP inmate locator. FBOP stands for Federal Bureau of Prisons.
If the searcher, on the other hand, is attempting to find someone who is located within a state's prison, then he or she should use the DOC locator for that state. DOC stands for Department of Corrections. Every state has its own Department of Corrections, so each state will have its own DOC inmate locator which only searches within the justice system of that state. On the other hand, the Federal Bureau of Prisons houses federal inmates, which means that it has prisons all throughout the nation. Thus, the FBOP inmate locator will search an entirely different set of prisons and institutions than will a DOC inmate locator.
The FBOP inmate locator is found on the website of the Federal Bureau of Prisons, and similarly, each state's Department of Corrections website normally has some form of DOC inmate locator. The FBOP inmate locator will search the 115 institutions that are within the FBOP system. The FBOP inmate locator can only find inmates who have been incarcerated from 1982 on. A DOC inmate locator will vary in how many institutions it searches and how far back it goes depending upon the state.