Submission of Matters to a Vote of Security Holders - Form 8-K

On May 8, 2024, the stockholders of Packaging Corporation of America ("PCA") approved the Second Amended and Restated 1999 Long-Term Equity Incentive Plan (the "Plan"). A description of the Plan was included in Item 3 of PCA's Proxy Statement for the 2024 Annual Meeting of Stockholders filed with the Securities and Exchange Commission on March 28, 2024 (the "Proxy Statement") under the caption "Summary of the Plan" and all sub captions thereunder, as supplemented by PCA's Supplement to Proxy Statement filed with the Securities and Exchange Commission on April 3, 2024 under the caption "Supplemental Disclosure Concerning Item No. 3." The full text of the Plan was attached as Appendix B to the Proxy Statement. Such summary and the text of the Plan are incorporated by reference into this Item 5.02.