We were just as surprised as you are about free camping near Banff. The Saskatchewan River Crossing is actually INSIDE Banff National Park and they allow overnight parking in their parking lot.

Parking overnight in a RV at The Crossing located at Saskatchewan River Crossing is completely free- they just ask that you stay one night only and only park in the gravel lot between 3PM and 9AM, which is PLENTY of time.

There laundry, a convenience store, gas, RV dump and water, and even a little restaurant/pub where you can have a couple beers and a massive plate of nachos. While the gravel lot you’re staying in might be a bit on the rustic side, the view is absolutely incredible and we found it quiet enough given the price. We’ve stayed in much worse for much more money ;)