UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q For the quarterly period ended March 31, 2024 Commission file number 1-32737 KOPPERS HOLDINGS INC. (Exact name of registrant as specified in its charter) Pennsylvania 20-1878963 (State of incorporation) (IRS Employer Identification No.) 436 Seventh Avenue Pittsburgh, Pennsylvania 15219 (Address of principal executive offices) (412) 227-2001 (Registrant's telephone number, including area code) | Title of each class | Trading Sy ...