Orion Nebula Cluster population

Approximately 50% of the ~3500 stars identified to date within ~2.5pc of the namesake Trapezium stars are optically visible, and in this paper we focus on that sample with I<2.5mag. The large number and number density of stars (n_peak_>10^4^pc^-3^), the wide range in the stellar mass (~0.1-50M_{sun}_), and the extreme youth (<1-2Myr) of the stellar population, make the ONC the best site for investigating: (1) the detailed shape of a truly "initial" mass spectrum; (2) the apparent age spread in a region thought to have undergone triggered star formation; (3) the time sequence of star formation as a function of stellar mass; and (4) trends of all of the above with cluster radius.