>GIS is probably one of the best things to happen to cartography in the last couple hundred years.

GIS is amazing, but the first and second world wars saw a lot of advances in cartography. I'd say #1 advancement goes to the near-perfecting of portable Theodolites. It's a telescope which allows you to look at one point, then look at another, and very accurately understand the angles between them. From that, with a little walking and Pythagoras, you can figure out distances, and thereby create accurate maps with relatively minimal effort and human-error opportunities.

I say "relatively minimal effort" because technique the portable theodolite replaced was sending battalions of civil servants out into the countryside with 50ft long chains and asking them to walk the length, height and breadth of the country.