The United States launch facility from which an orbital nuclear weapons platform was sent up in 1968, the target of Gary Seven's sabotage mission.
McKinley Rocket Base is the main Earth location of the Original Series episode Assignment: Earth.
When the Enterprise travels back to 1968 for historical research, it intercepts Gary Seven, a human agent trained by unseen aliens. His task is to interfere with a rocket carrying an orbital nuclear warhead platform, due to lift off from McKinley Rocket Base.
Seven slips past the base's security and climbs the gantry to rewire the rocket. Kirk and Spock, unsure of his motives, beam down and are arrested by the guards. In the end Seven detonates the warhead harmlessly high above the ground, frightening the powers into caution.