Why was the Declaration of Independence in the Appendix of the novel? What purpose did it have?

The Declaration of
Independence was in the Appendix of the novel because it was used as an example of how obsolete
these foundational documents would be in the face of the Party and Newspeak. One of the purposes
of the Party was to rewrite history and  make it a fluid idea, not something concrete. The Party
changed history on a daily basis to fit its purposes. The point of Newspeak was to limit the
range of thought of the society members so that they would be easy to control. In fact, Newspeak
limits thought so much that the society would not have to rely on the Thought Police when it was
fully in place and no one remembered Oldspeak because there would hardly be any way to express
dissension. The Appendix explains the principals of Newspeak and it's basically saying that all
things written prior to 1960 would not even be able to be translated into Newspeak so there
would be no fear of someone coming across a document that supported freedom and equality so
boldly to translate it and try and follow those principles. Any person reading the declaration
would translate the entire section printed in the appendix into one word,
"crimethink" because all one would be able to gather is that it
promotes ideas that are related to thought crime.