The United States (US) Department of Defense (DoD) Electromagnetic Pulse (EMP) protection standard offers a solid basis for protecting commercial communication, data, and control facilities. Because of the standard’s shielded barrier and test requirements, it is not surprising that there is a strong temptation within industry and government to dismiss the MIL-STD 188-125 approach in favor of less rigorous protection methods. It is important to understand that US DoD EMP protection standard for fixed facilities, MIL-STD-188-125, reflects an evolution by trial and error that spanned a period of decades beginning with the acquisition of the Minuteman Missile System in the 1960s. In fact, one of the main motivating factors for developing the standard was that system developers in the Air Force, Army, Navy, and Defense Communications Agency (now Defense Information Systems Agency) and the Federal Emergency Management Agency tried less technically-sound approaches that failed in their effectiveness, testability, and maintainability. This paper revisits the development of the US DoD standard and explains its provisions and underlying technical rationale. The paper’s objective is to enable the public officials and engineers involved in planning and implementing EMP protection for critical infrastructure facilities to avoid the pitfalls encountered in the past and use the best practices available to achieve low risk protection designs that can be maintained over the entire lifecycle of critical infrastructure systems.