X0508 4 2024-08-13 0000354190 Arthur J. Gallagher & Co. AJG 0001185998 CARY RICHARD C 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 Controller, CAO 0 Common Stock 2024-08-13 5 W 0 E 125 0 A 38438.75 D Common Stock 2025-02-10 4 S 0 1400 321.03 D 78373.749 D Common Stock 2025-02-10 4 S 0 2270 321.91 D 76103.749 D Common Stock 2025-02-10 4 S 0 1907 322.95 D 74196.749 D Common Stock 2025-02-10 4 S 0 3923 324.12 D 70273.749 D Common Stock 2025-02-10 4 S 0 500 324.63 D 69773.749 D Common Stock 367.551 I Gallagher 401(k) plan account The price reported is an average weighted price. The shares were sold in multiple transactions on 2/10/2025 at prices ranging from $320.54 to $321.53. The price reported is an average weighted price. The shares were sold in multiple transactions on 2/10/2025 at prices ranging from $321.56 to $322.53. The price reported is an average weighted price. The shares were sold in multiple transactions on 2/10/2025 at prices ranging from $322.56 to $323.51. The price reported is an average weighted price. The shares were sold in multiple transactions on 2/10/2025 at prices ranging from $323.59 to $324.58. The price reported is an average weighted price. The shares were sold in multiple transactions on 2/10/2025 at prices ranging from $324.59 to $324.76. 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 ranges set forth in the footnotes to this Form 4. /s/ Ryan Session, by power of attorney 2025-02-12