The Louvre in 1911 was an institution still adjusting to the concept of modern security. It employed hundreds of people on its enormous staff, many of whom moved through the building in white smocks — a standard uniform that indicated museum work. Access to the building outside public hours was loosely controlled. Workers, tradespeople, restorers, and maintenance personnel came and went on schedules that were not always carefully tracked. The logic was institutional and historical: French national museums were public cultural institutions. Their contents were the property of the republic. The idea that someone would simply remove a major work and walk out with it had no established precedent.
The Salon Carré, where the Mona Lisa hung, was open to visitors and had been for decades. The painting hung alongside other works. On any given day, visitors could walk past it at close range. They occasionally wrote letters to it. At least one person had shot himself in front of it in 1910, an incident that received press attention and reflected the intensity of emotional responses the painting provoked in some viewers. Custodians had long noted that the Mona Lisa attracted more unusual behavior from visitors than most other works in the museum.
The room was not watched every minute of every day. Guards patrolled. Workers moved through. On Mondays, the museum was closed to the public — a maintenance day when workers and authorized personnel could move through the building more freely than on public days.
The theft happened on Monday, August 21, 1911.