For the best possible answer, you should look at each separate state's specific instructions.

Try Handgunlaw. Click on: Handgunlaw.us

Steve is correct. I'd add one thing.... make note of the date that a given States' laws were posted. If it's a couple of years old, call the state police agency for that state and make sure of their laws. Get the name of who you speak to, or better yet, have them fax you the information. (sources are good things)

Most states have a "peaceable journey" law that covers you while traveling, but ignorance of the law/s will not be an acceptable defense if you have to interact with law enforcement for whatever reason.

the federal regs here

Code of Federal Regulations
Title 18 - Part I - Chapter 44 - § 926a
§ 926A. Interstate Transportation of Firearms
Release date: 2005-08-03
Notwithstanding any other provision of any law or any rule or regulation of a State or any political subdivision thereof, any person who is not otherwise prohibited by this chapter from transporting, shipping, or receiving a firearm shall be entitled to transport a firearm for any lawful purpose from any place where he may lawfully possess and carry such firearm to any other place where he may lawfully possess and carry such firearm if, during such transportation the firearm is unloaded, and neither the firearm nor any ammunition being transported is readily accessible or is directly accessible from the passenger compartment of such transporting vehicle: Provided, That in the case of a vehicle without a compartment separate from the driver’s compartment the firearm or ammunition shall be contained in a locked container other than the glove compartment or console. http://www4.law.cornell.edu/uscode/h...6---A000-.html

also known as "peacable journey" ONLY apply to travel THRU states and do not cover a stay in a state for any length of time. if you stop over night at a motel in a registration state, you are subject to arrest. read and understand the laws for every state you are traveling thru, know where the gun must be stored and in what condition.

also make sure the gun is legal, the magazine is legal, the bullets are legal and your ccw (if you have one) actually has reciprocity for each state you will be in.

remember, all the stuff you read here is great, but the responsibility is yours to apply it correctly, its YOUR a$$