I visited Glacier National Park for four days in August 2016. Grinnell Glacier is located in the Many Glaciers section of Glacier National Park, which is otherwise known as prime grizzly bear territory. Since this is one of the most popular trails in the park, it is heavily trafficked by hikers. So we weren't too concerned about encountering a bear.
Glacier National Park
Glacier National Park is located in northwestern Montana along the US-Canada border just south of Waterton Lakes National Park. Together these two parks formed the first ever International Peace Park to better preserve and protect the shared ecosystem along the Continental Divide. Spanning across a million acres, Glacier National Park is home to 25 active glaciers (although scientists estimate they will all disappear by 2030), 71 species of mammals (including the grizzly bear!), and 151 trails (totaling 1,200km). The Going-to-the-Sun Road, the park's only road that cuts through the park, offers exhilarating views as you're winding around, through, and over the mountainous terrain.