The Chilkoot River and Lake are stunning areas that get extremely busy from June to August, depending on the different salmon runs. There are runs of sockeye, pink and coho salmon through this river during different periods of the year, which bring in A LOT of brown bears, fishermen and photographers.
Make sure to bring your camera because if the salmon are running, you are pretty much guaranteed to see one (or more) bears.
Be bear aware and make sure you stay a safe distance from the bears. They may seem used to humans, but I know several people who have been charged by bears in this area due to the high amounts of salmon. We once camped at the Chilkoot Campground, and the next morning, there was a completely destroyed cooler scattered around the area. Our neighbours had forgotten to put it away, and a bear had destroyed it overnight. These bears are very used to humans, but they are also wild animals and need to be respected.