I have a four year old Morgan, not registered but mostly old government lines. I bought him when he was 6 weeks old for $300 basically to "rescue" him. The woman I had bought him from used to run a breeding farm but her health had really gone down hill & she wasn't able to keep up with things. She had an unregistered stallion running with a couple of registered mares and so ends up with a few babies each year that are not registerable. Fausto (the foal) hadn't had any human contact so was pretty much wild. The woman's grown son decided to be helpful by jumping onto him to force him in the trailer but that just sent them both tumbling on the ground. He ended up going right in on his own since his dam was already loaded (I took his mother home until he was weaned). He will still hop on a stock trailer just fine but he is afraid of men. None of that really pertains to my question but I thought I'd include his background. The woman said that her horses tend to be slow to mature, he now stands 15 hands which is a fine size for me but I am wondering if he will still grow taller. My sister bought a 4 year old Arab stallion hoping he would stay the height that he was but he grew at least another inch but likely 2 after that. My aunt has a TWH x mustang that stands about 15.1 as a two year old, does this mean he will be huge or do different breeds just grow at varied rates? I am interested to hear what others have experienced while raising horses & when to consider them fully mature.