Any US bank is required to fill out a form and report to the federal government any cash transaction over $10K as part of the 1970 Bank Secrecy Act in an effort to combat money laundering. Having been a commercial teller years ago, I personally filled out several of these on a weekly basis as standard operating procedure.

If your cash transaction was less than $10K, then it is none of their business. However, I will say that if you use a major bank with several locations, only some of them will be equipped to handle large cash transactions (well, they will take your money but may not keep enough cash on hand to give you that much). In my case, I recently needed about $30K in cash for some home repairs and my local branch could not handle the transaction. They called a larger branch a few miles away and they handled it for me. They knew I was coming, and it took awhile since tellers don't keep that much cash in their drawers so they had to go through their vault access procedures, the count had to be authenticated by a manager, and I made them both watch as I counted the cash in front of them.

Depending on your bank, tellers are encouraged/required to know/recognize large depositors for customer service purposes. When I was a teller, we received a couple of reports every morning to review. Once was an overdraft list so that we were aware if these customers visited, and the other was a large depositors and/or recent large transactions so we could be extra friendly/helpful to those customers.

After a long holiday weekend, the retail and restaurant customers were swarmed with cash. I'd have hundreds of thousands of dollars laying around the commercial window (drive up only) because I couldn't catch a break to check it into the vault. Funny thing is, after handling so much cash it lost its mystic (just looked like work when I saw it stacked up or when it came in with a large deposit).