Here is a question and answer from TSA's website:
In light of the above answer, put the cash in a money (jeweler's) pouch (bj21.com sells a good one) along with a letter from your lawyer stating that you are an individual who often engages in casino gambling and that is the entirely legal reason for your carrying a large amount of cash. Put the money pouch in a lockable briefcase, which you will carry onto the aircraft. Lock the briefcase. No matter what happens as you go through the screening process, TSA is not going to get into your briefcase because only you have the combination to the locks. If a TSA screener wants to look inside the briefcase, you will have to open it. If a TSA employee asks what is inside the pouch, just say "currency." Zip open the pouch and show the cash to the inspector without removing it. If the inspector wants to count it, immediately object and politely ask to speak with the inspector's supervisor. The amount of cash you are carrying is none of TSA's business unless you are on an international flight, in which case you are required to declare the cash if you are carrying more than $10,000. Print a copy of TSA's document titled "Currency Reporting" (find via web search) and carry that in your briefcase also. You should not have to show a TSA employee the law, but it's only one page and, uh, you know.
There are a couple of negative considerations to carrying the cash on your person as you go through the x-ray scanner. The TSA screener will insist that you hold the cash over your head while being scanned, thus advertising the fact to eveyone present that you are carrying a large bankroll. Also, should you fail the scan for some reason, or trigger a metal detector, a TSA inspector will pat you down. He will also insist on running the cash through the luggage x-ray scanner by hand. A $15-an-hour TSA employee will do it, not you, knowing full well that he is holding a large sum of cash. I am not altogether comfortable with that arrangement, but that is the way it is.
It is important that you avoid packaging your bankroll in a suspicious manner, such as sealing it in Zip-loc bags, for example. Drug dealers often do this in an effort to thwart drug-sniffing dogs. As indicated in the TSA answer above, you don't want to give the TSA inspector any reason to call a DEA investigator. But you are not going to have a problem, because your cash will be carried in a cash pouch, right where one would expect to find legal cash. It would also be a good idea to carry a copy of a recent tax return documenting your gambling activities. This will not do you any good with TSA, but may mollify a DEA investigator if, despite your best efforts, TSA calls them anyway.