The past, present and future of the giant bovine are front and center in a new exhibition as the country approaches its 250th birthday A bison herd on the American Prairie reserve roams at sunset on October 18, 2018, in Montana Amy Toensing / Getty Images They’re massive, shaggy and majestic—and best observed from a safe distance. The bison, North America’s largest land mammal, has long been an icon in the U.S. and hugely important to Native cultures. Officially named America’s national mammal in 2016, it is a perfect, beastly representative of the country’s natural history. As such, the Smithsonian’s National Museum of Natural History has created bison-centric exhibitions to coincide with the celebration of America’s 250th this year. Opening May 7, “Bison: Standing Strong” will run until May 2029 and chart the animal’s evolutionary history and relationship with Indigenous peoples, its rise and fall and its place in the future.…