The reporting requirement has been in effect since 1970. Per wiki =>
“The Bank Secrecy Act of 1970 (BSA) ~snip~ Specifically, the act requires financial institutions to keep records of cash purchases of negotiable instruments, file reports if the daily aggregate exceeds $10,000, and report suspicious activity that may signify money laundering, tax evasion, or other criminal activities.[2]
So the $10,000 today would have been about $1,200 in 1970.