Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock () or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Natural Entrance to Wind Cave. Changes in outside air pressure cause wind to blow in and out of the cave. The new manmade entrances to the cavern have wind-trapping doors to prevent disruption of the climate inside the cavern.
Public Domain.
