Mt. Rushmore sign-ins

I will be visiting the Rushmore area shortly. I see there are numerous sign-in kiosks. Can anyone tell me if signing in is mandatory? Thanks for any help you can give.

When I was there I didn't sign a visitors book. While you're in the area you may as well bag the highest peak in SD, Harney Peak; it just a few miles from Rushmore to the TH.

While signing in isn't 'mandatory', it is encouraged. Mainly because it provides a record of climber visits and use, which allows the climbing community a voice in Park policies.

Great. Thanks for the help. We will be sure to do so.