A recent question asked where is the eastern most point in the U.S. which leads to where does the sun rise first. The converse of that would be where does the sun set first. I am not sure that anyone or any organization looks at this.
The first place in the U.S. to see the Sunset is Pochnoi Point, Alaska which is just WEST of the 180 degree E/W meridian. It also makes it the most eastern point of the U.S. to experience sunrise/sunset. Confirming that I was correct. I did a little research and here is a link for you that provides further explanation and more information.