The Bastille had once been a notorious prison holding Voltaire and other political detainees. But by July 14, 1789 - now celebrated as Bastille Day and often considered a transformative event in the French Revolution - its inmate count had slipped to a grand total of seven: 5 criminals and 2 "madmen."
Interesting how, then as now, in Louis XVI's France and in modern American correctional facilities, mental illness becomes intermingled with the incarceration of criminal offenders. This was no surprise to Michel Foucault, whose books Discipline and Punish and Madness and Civilization could be considered companion pieces.
So why was the taking of this rather forlorn prison called the Bastille such a catalyst for grand historical change? The middle class shopkeepers and artisans ("sans-culottes") who took the Bastille were not there for a jail break. They were seeking arms and ammunition to protect themselves against the possibility that the king would use force to disband the nascent National Assembly.
When the sans-culottes arrived at the Bastille, its commander ordered his troops to fire on them. 98 people were killed in this barrage, but the enraged crowed broke through, captured the prison, decapitated the commander who fired on them, and distributed arms to the citizens of Paris. Momentous decrees by the National Assembly soon followed, seeking to give form to the ideals of "liberty, equality, and fraternity."