Gary Sherman recently did a post showing how QGIS has grown since his first version twenty years ago. In a nutshell, it grew from 2,173 lines of code to over 2 Million! I had to check that twice to be sure.
We are also so thankful for his work on this and the many other devs that have picked up where he left off.
Check out the full post on Spatialgalaxy.net.