The Digital Public Library of America brings together the riches of America’s libraries, archives, and museums, and makes them freely available to the world. On January 6, 2016, The New York Public Library enhanced access to all public domain items in Digital Collections so that everyone has the freedom to enjoy and reuse these materials in almost limitless ways.
“This site is a living database with new materials added every day, featuring prints, photographs, maps, manuscripts, streaming video, and more.”
Search the collection here: http://digitalcollections.nypl.org/
The collections holds material relevant to the study of Kent. For example, this view of Gravesend from The pictorial field-book of the Revolution, Vol. 2, issued 1777-1890: