I think this is the single best National Parks road trip you can take in September. Grand Teton → Yellowstone → Glacier → Banff → Jasper. Five parks, two countries, one unforgettable route. September is perfect with warm days, crisp nights, fewer crowds, fall colors lighting up the mountains, and wildlife everywhere from elk rut to bears foraging. You also get clear views and golden light for photography. Highlights include Snake River Overlook, Old Faithful, Going-to-the-Sun Road, Moraine Lake,