From the KGW Archives:
When President John F. Kennedy travelled to the Hanford Nuclear facility in September, 1963, it was to commision the newest reactor, named the "N" reactor, that had been built at the site.
[note: reactors and other facilities on the site were signified by a single letter of the alpahabet]
The Department of Energy's history of Hanford points to the importance of the event:
"N Reactor was so revolutionary that then-President John Kennedy came to Hanford in 1963 to commemorate the start of plutonium production operations as well as break ground for the power-generating component of the facility. His visit to Hanford was one of the few times when the Sites security restrictions were eased allowing a crowd of more than 30,000 people to visit the reactor and listen to the President's speech"
It was a significant moment in Northwest history not only for the Presidential visit but also because Kennedy used the event to illustrate his belief that the science and technology of nuclear energy could equally be used for national security as well as for building communities by providing much needed power to the fast growing region.
The President also references Hanford's past history regarding World War Two. What he was refering to was how the top-secret facility had produced the plutonium for the bomb used at Nagasaki, that in effect, brought and end to the war.
The date of the speech was September, 26th, 1963. President Kennedy was assassinated in Dallas, Texas, less than two months later on November 22nd.