Every state has its own nursing board and license. The ordinary thing to do when you want to work in another state is to apply for their license, costing time, hassle, and expense. About half the states are part of a nursing licensure compact, where if you live in one member state and hold a license, you may work in another member state without having to get their license, as long as you don't move there (the requirement to have a multi-state license is that you actually live in a member state - you can't get one if you live elsewhere, even if you hold a compact state license to work specifically in that state).
The impetus for the compact was not travel nursing. It had to do more with legal issues of cross state practice such as telephone or internet practice. It also allows better disaster relief. BTW, neither Florida or Louisiana are members of the compact but both have instituted rapid disaster licensure.
In my opinion, compact licensure, undeniably convenient for those travelers who reside in a compact state, is not a boon for travelers. One of the reasons that nursing pays relatively well is that we have barriers to entry - education and board examination mean that hospitals have restricted choice for staffing (a good thing for us, and patients). The same theory applies to free movement across state lines with licensure specific to that state. The best paying states, California, Oregon, Washington, Massachusetts, NY, and NJ have licenses that are relatively difficult to obtain and are not members of the compact and no signs that they ever will. In contrast, compact states generally pay lower wages. This is quite notable to many travelers.
Because of this, the politics of a state becoming compact are the opposite of what you would otherwise expect. The state nursing associations are opposed because they know it will help keep wages down. The hospitals and their state association are for it for the same reason the associations (and unions) are against it. These are slow trends to be sure and not the only factor, but compact status is certainly part of pay trends nationally.