It is legal to watch adult pornography.
The pornography that is illegal to watch or possess including images and videos is child pornography which is different from adult pornography.
Federal law defines child pornography as any visual depiction of sexually explicit conduct involving a minor (persons less than 18 years old).
Child pornography is a serious offense and can get you into trouble and in prison for years for watching, downloading, sharing etc.
But adult pornography is legal to possess, watch, share, download etc.
As long as the adults are consenting to the sexual acts in the adult porn and they are consenting to share that adult porn online or any other way, the adult pornography is legal.
As long as the porn is not child pornography or bestiality, there's no legal reason that pornography cannot be filmed anywhere in the United States.
It's also legal to produce and distribute amateur porn with multiple licenses and insurance but you will need a release in most states if doing it as a business.
But you can legally film yourself and your partner or another consenting adult engaging in sexual activities and legally place that porn on adult porn websites without a license.