This is my great-grandpa, Harry Robinson, with his horse, because the impulse of people to pose with their awesome machines is older than the Trans-am.
My Favorite Picture in the History of Pictures
Tiny Cat Pants
Is there anything funnier than tiny cat pants?
Tiny Cat Pants 
That is a magnificent animal, and it looks well-cared-for too. Kudos to your great-grandpa!
Wow. That horse is pure muscle. I’d be unable to resist posing with it too.
He was pretty fascinated with having the best farm animals. The family story is that he purchased an elephant from the circus once, figuring that, if a horse was good for farming, an elephant would be better, but my great-grandma made him take it back. I’m sad there’s not a picture to confirm the truth of that!
What everyone else said about the awesome horse.
Where did he live? I love the mountains behind them.
I sadly must report that this is Michigan and those mountains are actually just crinkles in the old photograph.