First Transcontinental Telephone call was submitted by a telephone of this type January 25, 1915. Mr. Theodore N. Vail, President American Telephone and Telegraph Company talked from Jekyll Island, Georgia to Mr. Alexander Graham Bell, inventor of the telephone in New York; Thomas A. Watson, assistant to Mr. Bell in San Francisco; and to President Woodrow Wilson in Washington, D.C.
Plaque courtesy Lat34North.com.
Original page, with additional info, here.
Photo credit: Tim Walleker.