Not too long ago at all, just about 150 years. That may seem like a long time, but when you consider that folks have been growing potatoes for around 4500 years in Peru, it took the world a while to figure out how to deep fry them and sell billions of chips.
French fries came first. They had been popular in France since the 1700s and came to America with Thomas Jefferson after his stint as an ambassador in France. The story goes that one night in 1853 at a fancy resort in Saratoga Springs, New York, a wealthy diner sent back his French fries, claiming they were too thick. The chef, an American Indian named George Crum tried to make a thinner fry but the picky patron sent those back too.
So then Crum got really fed up and sliced a potato so finely you couldn't even pick them up with a fork. Surprise--the guy liked them. So did everyone else, and they soon became known as Saratoga Chips. Crum went on to open his own restaurant but chips didn't become a widely available snack food until 1925 when a mechanical potato slicer was invented that could cut potatoes to 55/1000 of an inch. Waxed bags came along right about then, too. So next time you get to the bottom of a delicious bag of chips, and see Crum's crumbs, remember this story.