However, at most companies, there's no formal requirement that you do so. Most employment in the United States is called "at will", which means that your current employer can fire you at any time and for any reason (except those that are prohibited under law).
The Thank You. Next, it's always a good idea to thank your employer for the opportunity, describing some of the key things you've enjoyed and learned on the job. And yes, this is true even if you're thrilled to be leaving. Remember__you may need these people for a reference down the line, and leaving things on a good note will leave a lasting (positive) impression.