We present a detailed study of the young massive star cluster Westerlund 2 (Wd2) using a high-resolution multi-band survey observed with the Hubble Space Telescope.  With an estimated mass of ~4×104 M⨀, Wd2 is one of the youngest (~1 Myr) massive star clusters in the Milky Way and contains a rich pre-main-sequence population. We show that the mass accretion rate of the pre-main-sequence stars is reduced in proximity to the cluster’s massive O stars, which are eroding the circumstellar disks of the low-mass stars. We find that Wd2’s mass function is steeper than the canonical slope of the initial mass function. The cluster shows mass segregation, which is likely primordial given its young age.