Other differences also exist. For example, Maryland distinguishes between a "registered" massage therapist, who has 500 hours of training, and a "certified" massage therapist, who has an additional 60 hours of college credits and is permitted to practice in a wider range of settings. Also, there are states wherein regulation is done at the level of the town or city.
The other half of U.S. states have no credential requirements at all, although there's a lot of infighting about this. Check out the rubbers in your state at the National Certification Board for Therapeutic Massage and Bodywork Web site at http://www.ncbtmb.com.