Just FYI, it's a "license" (or "licensure"), not a "certification."
There are a few different concepts it's important to understand. First, you only have to pass the NCLEX once -- the exam itself is nationally standardized, and every US state will accept your results.
Second, each US state has the legal right to control the practice of nursing (and every other licensed occupation/profession) within its own borders. In order to practice within a given state, you have to be licensed in that state (or have a license that is recognized by that state -- more on that later). Once you are initially licensed in a state (in whatever state you start your career), when you want to move to or work in another state, you can apply for licensure in the "new" state and they will license you on the strength of your already being licensed in another state (this is called licensure "by endorsement"). You also have to pass a background check, and some individual states have some particular additional, minor requirements, but it's basically a pretty painless process -- mostly a matter of completing the paperwork and paying whatever big fee the new state charges.
Some US states have chosen to join the Nurse Licensure Compact (NLC), in which states agree to recognize other states' nursing licenses for work purposes. This means that you can use your license in your "home" state (if your home state is a member of the compact) to work
in any other "compact state" (state that has joined the NLC) for as long as you want -- but only as long as you maintain your permanent residence in your home state
. If you move
to another state, even another compact state, then you have to apply for a new license in that state. (There's a lot of confusion and misinformation out there about this ...) A "compact license" is most useful for people who work as traveling nurses or who live near the border of another compact state (I live on the border of my state, which is a compact state, and work in the "next door" state, which is also a compact state). For most
nurses, compact licensure doesn't really mean anything.
Not all states have chosen to join the NLC. Here is a current list of participating states: https://www.ncsbn.org/158.htm
Apart from the NLC, you need to have a state license for any/every state you practice in. You can hold as many licenses as you're willing to pay for.