Cygnus was one of the first constellations recognized by ancient civilizations, and because of its shape-- a short tail and long neck, it became associated with the swan. Pictured is Johannes Hevelius' Cygnus from Uranographia (1690). For more on the constellation, view material(1) from the Chandra X-ray Observatory, including the object known as Cygnus X-3, which Andrew Collins writes about.

1. http://chandra.harvard.edu/photo/constellations/cygnus.html