It's not illegal to travel large distances within the USA while carrying large amounts of cash. But it is extremely risky to do so because it can be seized by

It's not illegal to travel large distances within the USA while carrying large amounts of cash. But it is extremely risky to do so because it can be seized by any number of law enforcement agencies and will leave you with little to no recourse on getting it back. Somehow, law enforcement seems to be aware of when a large cash withdraw was made recently. The only time I was ever asked during a traffic stop, "are you carrying with you a large amount of cash" was about a week after I withdrew $12k from my bank account (and signed a buttload of forms for the privilege).