Why do banks report withdrawals over $10,000?

Anna State Bank 7 BANCORP Bank National Association 21 Bank of Baker 2 Bank of Lake Village 1 BANK OF OLD MONROE 7 BankVista 5 BAYVANGUARD Bank 16 Community State Bank, Rock Falls 4 First Central Bank, McCook 10 First Missouri Bank of SEMO 2 First National Bank & Trust, Elk City, OK 2 GBC International Bank 20 Grand Valley Bank 4 LIVE OAK BankG CO 11 PEGASUS Bank 14 REGIONS Bank 14 SouthernTrust Bank 8 State Bank of Whittington 12 TRI CITY National Association National Bank 12 Tristar Bank 18