I was arrested once for jumping over the turnstile without pay in ny, charged with a misdemeanor but was ultimately dropped. How will this affect my chances to get accepted into the marines officer candidate school?

I'm also in NY.

Why was the charge "dropped?"

This is a relatively minor charge - theft of services, most likely BUT the Marines want the best of the best. Only way to know is to ask and have the Marines "run" your record, make a determination.

If this was really dropped then there is no criminal record and no conviction, If you paid no fine, if you were not on any first offender program, if you did not do any community serivce, then it was dropped.

But the arrest will still show up most likely for the level of check the marines will and can do. So be ready to honestly explain this.

I would say that it may cause some issues, and if there are many other canidates even hurt your chances, but you can try, that is all you can do.