Yes the VIN must be visible at all times, I don't know of any state that doesn't require that. It is important because it is the only permanent way to identify a vehicle. (Permanent being a relative term as some VINs are on small plates that can, with some work, be removed. Changing a VIN without the proper paper work is also illegal. ) License tags can be easily switched, safety and environmental inspection stickers can be switched, registration stickers and papers, insurance and title papers can be switched. If the vehicles involved in the switch are same makes and models a 'casual' check may not catch it, but all those tags and documents also list the VIN. The VIN is the only way to verify the validity of the documents. That is important to the cop that wants to write you a ticket for no insurance, no registration etc., in identifying stolen cars, accident reports, and stuff like that. ( You got a parking ticket, the license number is listed on the ticket, you say " It wasn't my car, my friend with the same kind of car 'borrowed' my plates." But if the VIN is on the ticket, welllll....) The VIN is important in buying and selling cars, it verifies the bill of sale, title, and other documents, checking for recalls,accident history etc. The VIN is important in buying replacement parts, there may be what appear to be minor differences in parts for the same make and model, but the parts aren't interchangeable, the details of the VIN can determine those diffs. I can't help you on the penalty part, the helpful web sites that the States have about their laws are not all that helpful. ( You're pro'lly not interested in the laws about selling cars and such anyway.) Tickets for obstructed VIN are rare in traffic stops, you just move what ever is obstructing it. If it's obscured by something permanent, missing or altered you usually get a ticket concerning registration but you could wind up in a lengthier investigation concerning theft. Usually obstructed VIN tickets are given by parking enforcement . Those are usually city ordinances and the fines vary widely. In some places if your VIN can't be seen ( an envelope slid over it say) and your parked on the street, your car can be towed ! Most places won't let you use a car cover on the street unless the VIN is visible, they sell covers with a small hole over the VIN area, sometimes with a flap. In NYCity a cop is allowed to lift a cover to check the VIN, if he want's he could just have you towed cover and all. I found an interesting case(NEW YORK v. CLASS ) that involved a severe penalty for obstructed VIN that went all the way to the Supreme Court. The cops pulled over a car for speeding the driver got out of the car, and was trying to talk one of the cops out of giving him a ticket, the VIN was covered by some papers . One cop opened the car door to move the papers and saw a handgun almost hidden under the seat. The driver was charged and convicted of illegal possession, he was investigated for several other crimes in which a similar gun had been used, and convicted under some warrants that investigation discovered which the original traffic ticket would not have found. He appealed claiming unlawful search. The Court held that it was not an illegal search, the cop was acting legally when he reached in to uncover the VIN and did not violate the Fourth Amendment. So Mr Class served a lengthy prison sentence because of an obstructed VIN. Long answer huh? I got intersted in the research, sorry. The answer is Yes, it's got to be visible, it's important 'cause it identifies the vehicle, and the penalties range from a $25-$50 fine to the chair. So make sure them numbers is clearly visible or hide that roscoe better.

The requirement to have the VIN visible is a federal law and not state.

This is a violation of federal law. the vin must be visible, at all times, to allow law enforcement to check the vehicle for stolen. it also aids new and used car dealers in the identification of said vehicle. to obstruct a window vin, in most states, is a violation of the registration law. this law has several subsections, that deals with vins on motor vehicles. most people lock their vehicles. a locked vehicle does not give the police access to the vin on the drivers door to check for stolen, thus the window vin.