Ok fuckface, here's the law
http://codes.ohio.gov/orc/2923.16
There is more but it has more to do with if you are a gov employee or discharging from a motor vehicle. The gist of the law is that you may not have a loaded firearm accessible to you. If it is accessible and a long gun then it must be in plain site with the action open or disassembled. Handguns still can not be accessible, even in plain sight. It says nothing about whether or not it can be loaded if it is not accessible to you. It also does not say it must be in plain site if it is in a box or container or part of the vehicle that can not be accessed without exiting the vehicle. The law does not prevent you from leaving a loaded firearm in a closed package, box or case or in a part of the vehicle you can not access without leaving (assume trunk or truck bed). The law only states that you must inform an officer to having a firearm if you have a concealed weapon permit AND have a concealed weapon on your person.
So, going by the law that I quoted, the correct way to transport a firearm in a wagon is either in plain sight with the action open or the firearm disassembled, in which case in CAN be within reach like in the back seat (gun racks in pickups are legal after all) OR it must be in a closed package, box, or case. Doesn't have to be locked, and there is no duty to inform unless you are CCWing.
Again, my SUGGESTION is don't get pulled over, and if you do, don't volunteer unnecessary information. But then again, having your CCW means you can have a loaded handgun wherever you want in the car and its cool so long as you inform and don't make any attempt to touch it.
And for more reading material:
http://www.buckeyefirearms.org/Ohio-Gun-Laws