Enacted in 1970 and expanded many times, most heavily by the USA PATRIOT Act, the BSA is the source of most US financial surveillance obligations. It is administered by fincen, with examinations delegated to the banking agencies, the sec, finra and the nfa for their members.
Its core reports are the suspicious-activity-report and the currency-transaction-report. Its core process obligations are customer-identification-program, customer-due-diligence and the beneficial-ownership-rule for legal entity customers.
Structuring deposits to stay under reporting thresholds is a separate criminal offence, which is why breaking a large cash deposit into smaller pieces is a far worse idea than making the deposit.
Related: fincen, suspicious-activity-report, currency-transaction-report, customer-identification-program, anti-money-laundering