Everyone has given you an answer... and most are right.... but here are some thoughts for you....
You can get your CDL at age 18.... You are not allowed to run interstate.... You have to stay in the state you are licensed in
Second, you will probably have a very difficult time getting a job because of your age. Like everyone stated, it's an insurance thing. You are looking at age 21 for interstate and most companies that I have dealt with have a 23 year age minimum for insurance purposes.
There is no law that says you can't get your CDL and drive a truck, but the odds are against you for that job to happen. If you know a farmer or rancher that needs someone to haul grain, or livestock to the elevator or stockyard, you may get lucky. You might find an owner operator that will put you on running locally, but I highly doubt it. You are going to have a tough time getting your foot in the door, but that doesn't mean that it can't be done....
I have been looking at life through a windshield for over thirty years... with no accidents or violations.... 2.5 million miles... I have also trained more people how to drive one than I can remember. It is not just a job, but a lifestyle. It can be very rewarding, but also can be very lonely. You have to enjoy your own company... :-}
Good luck to you in your pursuits.