Isabella Stewart Gardner Museum theft

On March 18, 1990, 13 paintings worth for a total of $500 million were stolen from the Isabella Stewart Gardner Museum in Boston. In the early hours, guards admitted two men posing as police officers responding to a disturbance call.
Once inside, the thieves tied up the guards and over the next hour committed the largest-value recorded theft of private property in history. Despite efforts by the Federal Bureau of Investigation (FBI) and multiple probes around the world, no arrests have been made and no works have been recovered.
The museum initially offered a reward of $5 million for information leading to the art's recovery, but in 2017 this was temporarily doubled to $10 million, with an expiration date set to the end of the year. This was extended into 2018 following helpful tips from the public.