Canisters are also required in Rocky Mountain and Grand Teton National Parks, and in an increasing number of sites in Olympic National Park. North Cascades National Park is phasing in mandatory use of bear canisters starting this year. There are some areas of the Adirondacks where they are also required, and the Bear Vault is a no-no there because at least one bear has learned how to open it. There is also a short section of the Appalachian Trail in Georgia where canisters are now required, but it's easy for thru-hikers to hike through this short stretch in a day. Those are the ones I know about; I'm sure there are others!

It has always been a close race between human technology and the amazing learning capacity of bears (most of whom are "smarter than your average bear"). Containers that 30 years ago were considered "bear-proof" are long since gone!