I grew up hunting CO and we have been limited to a single deer per season with a few exceptions in the last 25-30 years. We have to apply for a deer tag (they are all on quota) in Apr and have to decide if we want a buck or a doe at that time. If you get a tag it is for a single deer. There are some bonus type tags but again, they are all limited. The normal annual bag limit for deer is one.
It wasn't until I started hunting whitetails after entering the Navy that I was ever allowed to take more than one deer a season. I almost didn't know how to act the first time I actually took two in one hunt. Many Eastern and Southern hunters don't know how good they have since they can take more than one a season.