I know that Iowa has a Junior PGA league that travels across the entire state, with a championship and All-Star event at the end of the year.  I would just do some research.  Look on Google, and also check at your clubhouse to see if they know of any junior events.

There will be local events at nearby municipal/public courses.  At 15 if there are no junior programs, you can still play with the adults, focusing on playing the best you, not whether you can beat the local with the 1 handicap  The USGA.org site has lots of information and links about the rules of competition.  From that site for the links for juniors, there is this link for competition at the junior level - http://www.juniorlinks.com/Detail.aspx?id=471.

If there are schools in your area that do offer golf, often students one school without a program in that sport can participate at another school.  You would need to be able to travel to that school for team events.

Find out if any organizations in your area have local junior tournaments or tours you can join. 

I just joined the Golf Channel Am tour this week. gcamtour.com check it out. The had a tournament at my local coarse last summer and I was VERY impressed.     HOOVY

There are many junior tours around the country that you can participate in if you are in high school.  Some include, the AJGA tour, and the FCWT tour.  You should do some research to see what tournaments there are in your area.  

Hey Andrew, thats a great question to ask and I can almost gurantee that if I cant answer your question then another TT member will be able to or a staff member will. One thing you can do is check with your local courses and see if they have any Junior teams or Tournaments for Junior Golfers. You can also get a USGA membership so that you can compete in tournaments. There might be some organizations that can get you going in Tournament golf, just ask your local pro shops or courses. Finally you should be able to join a Mens club at your course when you turn 18. That will get you going with your competiveness. Best of luck to you. Feel free to ask questions anytime on here.

Respectfully, Manny M.

You state has a state golf association. Contact them, most states have a junior tour.