X0508 4 2024-02-14 0000354190 Arthur J. Gallagher & Co. AJG 0001222374 HOWELL DOUGLAS K 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 VP & Chief Financial Officer 0 Common Stock 3165 I By Spouse Common Stock 292.455 I Gallagher 401(k) plan account Common Stock 2024-02-14 4 S 0 7000 238.626 D 95941.5662 D Common Stock 2024-02-15 4 S 0 5000 239.15 D 90941.5662 D The reporting person has no voting or invesment power over these shares and disclaims beneficial ownership. The price reported is an average weighted price. The shares were sold in multiple transactions at prices ranging from $238.80 to $239.50. The reporting person will provide to the Securities and Exchange Commission staff, the issuer, or any security holder of the issuer, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. /s/ Ryan Session, by power of attorney 2024-02-16