How old do you have to be to get a hotel room?

Im going on a trip to a zoo and plan on staying overnight.How old do you have to be to get a hotel room?
Depends on the place most places are 18 but some places like las vegas casinos you have to be 21.How old do you have to be to get a hotel room?
In the United States, 18. If you're with an adult (someone 18 or over) you can be any age. You also have to show ID. In most other countries it's 15 or so.
21