Mapquest would beg to differ. To me, the interface was the killer feature for Maps. The data and trip planning functionality existed already on the web (as my print outs of driving routes in the late 90s can attest to). But being able to just scroll around a new city was amazing. Every other site required clicking through every North or West button with a round trip to the server.

It wasn’t until later that the satellite data and street view data became the next killer feature.