One of the earliest known treaties to be recorded in writing is the one between the Hittites and the Egyptians following the Battle of Kadesh, in around 1280 B.C.  The Treaty of Kadesh was written in Akkadian cuneiform and Egyptian hieroglyphs. 

English Bill of Rights (1689)

American Colonial Charters
    (a link to Yale University's Avalon Project)

American Declaration of Independence (1776)

The American Constitution
    (a link to the National Archives hyperlinked version)

Treaty and two conventions relating to Louisiana Purchase (1803)

Fort Laramie Treaty with the Sioux, 1868
    (note the provisions stressing the importance of civilizing children and providing them with an "English education")