I began my search by taking two words two words that truly stood out to me when looking at the Ngrams from Dr.Kings Speech and The Declaration of Independence. These two words I chose appeared, in my research, to be the two most common, words that both documents shared. These words were Nation and Rights.
I started by looking for peak periods using the word Nation in News Print, with the Chronicling America data base. I found peaks around the times of both world wars, but a particular peak after WWI. I believe this was caused because of the redefinition of so many different nations after the war. This article I found was just as the war was coming to an end in 1918. It is a call for Americans to stand together and to realize that our idea of nationhood, and fighting this war, should transcend political hurdles. Furthermore it went on to point out less fortunate nations embroiled in the heart of the conflict in Europe. A unified America could help end the war, was its conclusion.
My second search, for the term Rights, found a lot of usage in during and around the Civil War. A found a very interesting article from and Indiana newspaper, that was an entire page OpEd more or less, about the natural rights of human beings. The writer argued through and through against the southern cause and condemned them for their practices. Indiana was a swing state, by the way, not as heavily in favor of this change. In the end it makes sense to find the term Rights used so heavily in this time period, but it is amazing some of the articles one is able to find by simply searching.
