Dg, The OP asked for info on the laws of specific jurisdictions. But do you really think being good to go in "most states and municipalities" is not gong to help him in the District of Columbia if he is out of compliance with its law?
All of which is why I was careful to use the qualifier "most
". Obviously, there are countless exceptions to the "rule" and it is always incumbent for any traveler carrying any kind of a firearm to be aware of the law(s) of specific jurisdictions regarding same.