(New York), May 31, 1878. 20 pp., on legal size paper. Agreement between Edison and the Western Union Telegraph Company giving Western Union full control in the United States of Edison's patent on the "improvements on Speaking Telephones...Speaking Telegraphs...Acoustic Telegraphs...Inventions in Acoustic Telegraphy..." and other improvements relating to his communication technologies. Signed by Edison and countersigned by Norvin Green, President of Western Union, and A.R. Brewer, Secretary of Western Union, as well as notes by Clarence Cary, notary public. Docketed on verso. Disbound, but with blue binding ribbon present; minor soiling.