US DOT Numbers

When you go to court, you will need to make the case your vehicle is not used in commercial operations. Show that the ladder rake is for your personal use and is not used to further some business interest. Make that case effectively and you will be mostly out of the woods. I am not sure if this is a fine or misdemeanor. If it is a misdemeanor you will have the option of a court hearing or an actual jury. I would pick the court, simply because it is much easier for a judge to understand the particulars of the law than it would be to educate a jury.

I would spend some time on the probable cause for the stop. Having out of state plates with a ladder rack sounds pretty weak as basis for the stop. Commercial cops have a lot of latitude, but if you don't have signage on your pickup, I don't understand his leap to judging you as a commercial business operating in his State. If you work for someone else as a contractor in your home State which is why you have the ladder rack, I would bring pay stubs showing your employment for the contractor, along with perhaps the contractors corporate structure that shows you are not an owner, just an employee who was on your personal time in Iowa.