Here are a couple of links that may help.
A lot of the laws were put in place a long tome ago. In my state straight razors are exempt because at the time the initial state law was written, most men shaved with one and the police couldn't arrest every traveling salesman or railroad porter that happened to have one. The laws are kind of Byzantine in nature, in that in some areas you can carry a bowie knife openly but nothing hidden. In NYC, you can carry a 4 inch blade as long as it is hidden. You really have to check by area.