Critical Infrastructure Protection: DHS Actions Urgently Needed to Better Protect the Nation's Critical Infrastructure, Statement of Tina Won Sherman, Director, Homeland Security and Justice, Testimony Before the Subcommittee on Cybersecurity, Infrastructure Protection, and Innovation, Committee on Homeland Security, House of Representatives [open pdf - 1MB]
From the Highlights: "The nation's critical infrastructure consists of physical and cyber assets and systems that are vital to the United States. Their incapacity or destruction could have a debilitating impact on security, national public health and safety, or national economic security. Critical infrastructure provides the essential functions--such as supplying water, generating energy, and producing food--that underpin American society. Protecting this infrastructure is a national security priority. GAO [Government Accountability Office] first designated information security as a government-wide high-risk area in 1997. This was expanded to include protecting (1) cyber critical infrastructure in 2003 and (2) the privacy of personally identifiable information in 2015."
Government Accountability Office: https://www.gao.gov/