@ajstringham I know how you feel. I'm 21, turning 22 in December. I've been here for almost 4 years now, and I'm still the youngest... however, I'm no longer the junior as far as responsibilities go
That said, I have a side-kick starting in December who will be just out of school, and I will no longer be the youngest person in the company. Yay!
It's not just 'in my company' either - I went to a seminar for ERP software last week, I was a good 20 years younger than everyone else there. I just made sure to speak up, nod my head and show I knew what I was on about