There was a real-life Grizzly Adams (but very different from the 1970s TV character). John Adams was born in Massachusetts in 1812 and went West for the California Gold Rush. After failing at a number of trades, he began training and showing grizzly bears.
But a wild bear put an end to things. Adams was attacked in the California Sierras in 1855, suffering severe head and neck injuries. He survived, but the wounds never fully healed and he died five years later. Showman P.T. Barnum reportedly paid for his gravestone.