Mclean Creek free camp or Wipress are both expansive, full of nature and cost nothing to stay at.
Just pack your garbage up after and try not to freeze your butt off
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I prefer Mclean, 45 mins away from Calgary and there is a pay to camp within 5km so you can stop @ the store if need be. Look up Mclean Creek campground, instead of turning right into the pay to camp you take a left over the cow gate and follow the road.