The earliest timelines, published in the 1500s and 1600s, were difficult-to-follow mashups that attempted to place all of human history into a list of numbers or an elaborate graphical metaphor. (I imagine the people who made these being somewhat stoned ... "So the fourth millennium before the birth of Christ was totally like a dragon! Here, let me show you ...")
By the 19th century, though, the art of the timeline had progressed significantly, and people like French engineer Charles Joseph Minard were creating infographics that look recognizably like infographics. This one, from 1869, traces the routes taken by Hannibal on his march through the Alps and Napoleon on his march into Russia, showing, through the thickness of the bars, how both armies dwindled during the journey.
This is from a great collection of historic timelines published on The Morning News website. Definitely worth flipping through the entire slideshow!
Via Philip Bump