In 1911, Boston Mayor John Fitzgerald began plans for a free zoo in Franklin Park. The Franklin Park Zoo opened to the public in late 1912 and was a great success, with millions of people visiting it each year. It differed from most zoos, as there were no front gates, and they spread the exhibits throughout the park.

The zoo was expensive to maintain, and because of the Great Depression and World War II, public funds were needed elsewhere. The zoo fell into disrepair and in 1958, the Metropolitan District Commission (MDC) took the zoo over. They put up fences and started charging admission. The new main entrance was by the Zebra cages, which is across the park from where the bear cages are located. 

They built new cages for the bears within the fenced area, and left the original bear cages to rot as they were deemed too expensive to take down. In 2003, the cages were used as a filming location for “Mystic River” starring Sean Penn. His character’s daughter, Katie, is found murdered in the abandoned bear cages. The old bear dens are listed on the Franklin Park website and are connected to various walking trails within the park.