UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-Q (Mark one) þ QUARTERLY REPORT PURSUANT TO SECTION 13 or 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended March 31, 2019 or o 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 1-15202 W. R. BERKLEY CORPORATION (Exact name of registrant as specified in its charter) (State or other jurisdiction of (I.R.S. ...