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( Mark One ) X SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 Form 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 or 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from Title of each class Delaware ( State or other jurisdiction of incorporation or organization ) 475 Steamboat Road ( Address of principal executive offices ) Commission file number 1-15202 W. R. BERKLEY CORPORATION ( Exact name of registrant as specified in its charter ) Common Stock , par value $ .20 per share 5.900 % Subordinated Debentures due 2056 5.750 % Subordinated Debentures due 2056 5.700 % Subordinated Debentures due 2058 5.100 % Subordinated Debentures due 2059 4.250 % Subordinated Debentures due 2060 4.125 % Subordinated Debentures due 2061 to Greenwich , CT Registrant's telephone number , including area code : ( 203 ) 629-3000 Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) WRB WRB - PC WRB - PD WRB - PE WRB - PF WRB - PG WRB - PH 22-1867895 ( I.R.S. Employer Identification Number ) 06830 ( Zip Code ) Name of each exchange on which registered New York Stock Exchange New York Stock Exchange New York Stock Exchange New York Stock Exchange New York Stock Exchange New York Stock Exchange New York Stock Exchange 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 > No Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15 ( d ) of the Act . Yes No 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 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 during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No