UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 _______________ Form 10-K þ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2018 or o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission File Number 1-2328 ______________________ GATX Corporation (Exact name of registrant as specified in its charter) New York 36-1124040 (State or Other Jurisdiction of incorporatio ...