It most definitely is legit. I should add that my dad has had his own practice for almost 30 years now, but for what is worth I only missed four-five sick days of school from kindergarten through 12 grade and my dad gave me many adjustments over the years.
His practice is mainly
Contact Reflex Analysis (I saw the negative hits on google and have to heartily disagree with most of them from my own observations and experiences) and nutrional supplements now though, as he very rarely uses his x-ray machine and has moved away from traditional Chiropractic quite a bit.