Jacob Harris, for the Atlantic:
This is the story of how I ended up captivated by a chance encounter with a 135-year-old newspaper advertisement — and how the random face staring back at me from the archives would reveal the surprising origins of ASCII art, a graphic design technique that’s usually associated with 20th-century computer art.
I’m not sure if this 1881 advertisement is truly the origin of ASCII art, but it’s certainly the oldest use I’ve seen. There are older examples of text laid in a specific shape, but none that I can find of a repeating letter used as a pattern element.
Update: Via Wikimedia, these ads in the Brooklyn Daily Eagle from 1875 predate Harris’ discovery.