Mt. Rushmore, why is there two?

I was doing a search on national monuments and I came across Mt. Rushmore. I did a google maps search and got Portland OR. Of course at first I was skeptical and so I did a street view. Sure enough there it was. but then Later I found the same thing in Keystone, SD. Which one is the real one? and if they’re both National monuments. Why do we have two?

Duh! Portland OR. never heard of this one, the actual one is in SD. I suspect that if you look you will find that the one in Portland (if it exist) is a scale model or just the name of a local mountain. Ok you win you made me look. Wikipedia only shows the one in SD.