We present the Two Micron All Sky Survey ( 2MASS ) ( J - K , K ) color-magnitude diagram for the region within 1 \arcdeg of the center of the Sagittarius dwarf spheroidal galaxy .
Using the slope of the red giant branch ( RGB ) , we determine a mean metallicity for the main stellar population of [ Fe/H ] = - 0.5 \pm 0.2 .
The Sagittarius RGB possesses a blue tail that overlaps with the foreground Milky Way giant branch , and suggests that \sim 1/3 of the RGB is more metal-poor than [ Fe/H ] \sim - 1 .
Direct comparison to the Large Magellanic Cloud confirms the metal-rich nature of the bulk of the Sagittarius population .
Our result is marginally consistent with the even higher metallicities determined from high-resolution spectroscopy .