the transportation of any (repeat, any) amount of currency solely within the borders of of the united states and its territories is completely legal-period.
any transportation of currency, foreign currency equivalent, or other negotiable instruments) whose value is greater than $10,000 u.s. is legal as well
provided you fill out the proper paperwork.
from the actual instructions...
WHO MUST FILE:
(1) Each person who physically transports, mails, or ships, or causes to be physically transported, mailed, or shipped currency or other monetary instruments in an aggregate amount exceeding $10,000 at one time from the United States to any place outside the United States or into the United States from any place outside the United States, and
(2) Each person who receives in the United States currency or other monetary instruments In an aggregate amount exceeding $10,000 at one time which have been transported, mailed, or shipped to the person from any place outside the United States.
A TRANSFER OF FUNDS THROUGH NORMAL BANKING PROCEDURES, WHICH
DOES NOT INVOLVE THE PHYSICAL TRANSPORTATION OF CURRENCY OR
MONETARY INSTRUMENTS, IS NOT REQUIRED TO BE REPORTED.
if anyone from the tsa ever questions me about having a large amount of currency, my response will simply be...
do you know what the law regarding currency transportation is?"
"are you a law enforcement officer?"
"am i under arrest"? (bonus points as it's a trick question for them)
"would you please bring the tsa terminal manager over along with a local or federal law enforcement officer"
"thank you, i'll wait for them right here if you don't mind"