As a parent, I've check my states registery of sex offenders to find how many live in my area. It listed the conviction, the law they were convicted of breaking. Most of the ones I saw were convicted or 2-3 crimes over 10 years. Since those convicted aren't required to register, it's not complete but it's still worth looking at.
Every parent should check their area. You might think twice about letting your 10 year old walk to the store or a friends house without supervision.