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Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K X Annual Report Pursuant to Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 For the fiscal year ended : December 31 , 2020 Transition Report Pursuant to Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 For the transition period from to Commission file number : 001-13221 CULLEN / FROST BANKERS , INC . ( Exact name of registrant as specified in its charter ) Texas ( State or other jurisdiction of incorporation or organization ) 111 W. Houston Street , Or ( Address of principal executive offices ) San Antonio , Texas Title of each class ( 210 ) 220-4011 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) CFR 74-1751768 ( I.R.S. Employer Identification No. ) 78205 ( Zip code ) Common Stock , $ .01 Par Value Depositary Shares , each representing a 1 / 40th interest in a share of 4.450 % Non - Cumulative Perpetual Preferred Stock , Series B Large accelerated filer X Non - accelerated filer CFR.PrB Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes No □ No No × Name of each exchange on which registered New York Stock Exchange New York Stock Exchange Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( §232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company , or an emerging growth company . See the definitions of “ large accelerated filer , ” “ accelerated filer , ” “ smaller reporting company , " and " emerging growth company , " in Rule 12b - 2 of the Exchange Act . Accelerated filer Smaller reporting company Emerging growth company 000