July 17, 2019, Mr. J. Michael Walsh delivered notice of his resignation from the Board of Directors (the Board") of Core-Mark Holding Company, Inc. (the Company") to Mr. Randolph I. Thornton, the Chairman of the Board, effective August 16, 2019. Mr. Walsh has served as a member of the Board since August 2004, and previously served as President and Chief Executive Officer of the Company from March 2003 to January 2013.