In 2015, I was just starting to get into map Twitter and was following a lot of people from Mapbox and other geo* companies. I was impressed with John Firebaugh's D3.js animations he was making, so I decided to do the same things with maps.
Mapbox Studio (Classic)
I had just learned about Mapbox's development version of Tilemill 2 (now Mapbox Studio Classic) and was playing around with CartoCSS and loving it. I wanted an excuse to mess with maps every day, and thus the "Tile-a-Day" project was born!