Remove or open up an interior wall
If the wall is load-bearing, a permit and engineered drawings are required. If you are not certain whether it is load-bearing, assume it is.
Permit rules are set locally, so the ZIP decides which state code applies and which office you would be dealing with. We use it to look up the jurisdiction and nothing else.
Why nobody can just tell you
Permitting in the United States is run by thousands of separate authorities, and each one can amend the code it adopts. Any site giving you a confident yes or no for every address in the country is guessing, and you cannot tell which answers are the guesses.
So this does not pretend. Each answer is the typical rule, where it comes from, and the thresholds that would flip it — plus a route to the office that actually decides. How this works.