Campsites were full as of yesterday. There is a camp fee if not full. Any BLM land is free camping if you can find any. There are a few free spots in Woodland Park near the McDonald's if you're up for a drive. Can't promise there will be any available as it is summer and peak tourist season.
Just did the same thing 2 days ago however we got lucky and there was one spot left
They make you reserve campsites ahead of time. Not sure how closely they watch though.
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