In yet another interesting historical computing highlight, we have the 1887 US dollar bill to thank for why we have 80 characters per terminal line as the current default terminal size:

[The first punchcards measured] 3.25 by 7.375 inches, the same size as the 1887 US paper currency because Hollerith [the inventor of the cards] used Treasury Department containers as card boxes.

Then, in 1928, IBM introduced the “modern” 80-column punch card with the same 3.25" x 7.375" physical size as Hollerith’s original cards; it looks like 80 was a round number of columns that was just about the largest they could fit in that physical space. This in turn led to the first computer terminals also having 80 characters per line, and the rest is just tradition.

(via Programmers StackExchange)