Alan Cressler:
Asclepias pumila, Devils Tower National Monument, Crook County, Wyoming 1
Alan Cressler:
Asclepias pumila, Devils Tower National Monument, Crook County, Wyoming 2
Alan Cressler:
Asclepias pumila, Devils Tower National Monument, Crook County, Wyoming 3
Alan Cressler:
Asclepias pumila, Devils Tower National Monument, Crook County, Wyoming 4
Alan Cressler:
Asclepias speciosa, Devils Tower National Monument, Crook County, Wyoming 1
Alan Cressler:
Devils Tower, Belle Fourche River, Devils Tower National Monument, Crook County, Wyoming 2
Alan Cressler:
Devils Tower, Belle Fourche River, Devils Tower National Monument, Crook County, Wyoming 3
Alan Cressler:
Devils Tower, Devils Tower National Monument, Crook County, Wyoming 1
Alan Cressler:
Devils Tower, Devils Tower National Monument, Crook County, Wyoming 2
Alan Cressler:
Devils Tower, Devils Tower National Monument, Crook County, Wyoming 3
Alan Cressler:
Devils Tower, Devils Tower National Monument, Crook County, Wyoming 4
Alan Cressler:
Devils Tower, Devils Tower National Monument, Crook County, Wyoming 5
Alan Cressler:
Devils Tower, Devils Tower National Monument, Crook County, Wyoming, Russell McLester 1
Alan Cressler:
Spearfish Formation Outcrop (Permian–Triassic age), Belle Fourche River, Devils Tower National Monument, Crook County, Wyoming 1