It is a very small campground. Only 5 sites. We were there the last weekend in September 2024. It was full when we arrived late in the day. We ended up dispersed camping a mile or two back up the trail along what looked like a logging road. We got up the next morning and a couple sites were open. We used a campsite to grab some breakfast, double checked our gear, use a restroom, etc. Then parked in the lot and left. It looked full when we returned a week later at the end of our trip, too.
McFarland Lake Campground As I was looking at the info for the campground, it looks like this may be a Minnesota State Forest and not a National Forest. Dispersed camping is legal on Minnesota State Forest Lands, but you need to know the rules.
Minnesota State Forest Dispersed Camping Info