X0508 4 2024-09-13 0000354190 Arthur J. Gallagher & Co. AJG 0002022545 Pesch Michael Robert 2850 GOLF ROAD ROLLING MEADOWS IL 60008 1 President 0 Common Stock 2024-09-13 4 M 0 7100 70.74 A 40367.04 D Common Stock 2024-09-13 4 S 0 7100 296.20 D 33267.04 D Common Stock 12505 I By Spouse's Trust Common Stock 368.46 I Gallagher 401(k) plan account Non-qualified Stock Option 70.74 2024-09-13 4 M 0 7100 0 D 2025-03-15 Common Stock 7100 0 D The price reported is an average weighted price. The shares were sold in multiple transactions at prices ranging from $296.13 to $296.58. 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. Shares held in irrevocable trust, of which his spouse is sole Trustee. Grant date of 3/15/2018. One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date. /s/ Ryan Session, by power of attorney 2024-09-13