This list from the General Services Administration is the US government’s official list of .gov domains (there are undoubtedly others that aren’t publicly admitted, as well as many public .gov sites that are missing). Many of the domains registered to intelligence agencies are extremely obscure. Below, I’m listing all of these domains as clickable links. Not all of them are working websites.
Registered to the CIA:
Registered to the NSA:
Registered to the Defense Department (NSA, NRO, DIA, etc.):
Registered to the Office of the Director of National Intelligence: