Which military rank is the highest among the listed ranks: E-1 through E-9?

The highest military rank among the listed options is Sergeant Major. In the ranking system, the E-9 level represents the highest enlisted ranks, and there are specific distinctions under this category. The Sergeant Major typically holds a significant leadership role, often serving as the senior enlisted advisor to a unit's commander. This rank carries considerable responsibilities, including mentorship and the overall welfare of enlisted personnel within the command.

Corporal and Sergeant are lower ranks within the E-4 to E-5 range, while First Sergeant, although a respected position, is still classified as an E-8 rank. Thus, the distinction of Sergeant Major as an E-9 makes it the highest rank among the choices provided, embodying both rank and authority critical to military operations.