I just saw this question asked about the state of Texas, and I was curious about what the law is for my state of PA.
Also, what if you’re recording ‘across state lines?’ How does the law work if you’re recording a conversation with someone in a different state? Wouldn’t that make it a federal matter?
In short: No, it is not legal.
Pennsylvania’s wiretapping law is a "two-party consent" law. Pennsylvania makes it a crime to intercept or record a telephone call or conversation unless all parties to the conversation consent.
If it’s across state lines, this still applies, however the person on the other end may be allowed to record according to their state’s rules. There have been some cases where cross-state laws are strange, but this is applied for businesses and their customers, private conversations are far too hard to even attempt to impose such a regulation on across state borders.