  We present V, I photometry of the Sagittarius Dwarf Spheroidal galaxy (Sgr)
for a region of ~ 1^{circ} times 1^{circ}, centered on the globular cluster M
54. This catalog is the largest database of stars (~500,000) ever obtained for
this galaxy. The wide area covered allows us to measure for the first time the
position of the RGB-bump, a feature that has been identified in most Galactic
globular clusters and only recently in a few galaxies of the Local Group. The
presence of a single-peaked bump in the RGB differential Luminosity Function
confirms that there is a dominant population in Sgr (Pop A).
  The photometric properties of the Pop A RGB and the position of the RGB bump
have been used to constrain the range of possible ages and metallicities of
this population. The most likely solution lies in the range -0.6 < [M/H] <=
-0.4 and 4 Gyr <= age <= 8 Gyr.
