In DC, NJ, IL, MO and several other states or jurisdictions, you would be in less trouble commiting an asault or robbery than you would be as a law abiding citizen caught carrying a legal weapon. Of course this statement is an oxymoron because there is no such thing as a legal hand gun in NJ, DC and most of the northeast.
Good luck and happy traveling - just don't get caught carrying a firearm illegally. You will be shocked and amazed to see how easy it is to carry a weapon illegally in most jurisdictions. If you follow the law, you may as well leave the weapon at home for the good it will do you if you are accosted. In most jurisdictions, you will have to retreive the weapon from its locked case in the trunk of your vehicle or some other area inaccesible to the driver. You must then retreive the amuntion or magazine from some other 'secure' location. Then you can assemble your defense and protect yourself.
If you own a gun and you do not belong to and support the NRA with your money and vote - you are an idiot.
Remember - the government wants you to believe you can call 911 any time from any location and politely ask the criminal to wait until police arrive.