Oswald Cobblepot (Earth-1: Pre-Crisis)

O. Cobblepot was the former mayor of Gotham City and a patient at Arkham Asylum.

Mayor of Gotham City
At some point, O. Cobblepot was elected as the mayor of Gotham City and at some point during this tenure, firing squads became a method of execution for death row inmates.

Incarcerated at Arkham Asylum
At some point afterwards, he was incarcerated in cell number 341 at Arkham Asylum. John Deegan later opened all of the asylum's cell doors which allowed the inmates to escape their cells until The Flash returned them.