Gang Hideouts are a special Collectible in Red Dead Redemption 2 (RDR2). They are available only after finishing the Story Missions. Players must visit these 4 out of 6 locations to complete the "Gang Hideouts" Trophy / Achievement.
Gang Hideout Locations of RDR2
How to Track Gang Hideouts Progress
Gang Hideouts cannot be missed and can be visited in any order at any time after completing the main story (epilogue of Story Missions).
You can track your progress in your menu by pressing Options > Progress and accessing the "Total Completion" menu.
Gang Hideout Location Maps RDR2