  We present Chandra X-ray images of the NGC 2237 young star cluster on the
periphery of the Rosette Nebula. We detect 168 X-ray sources, 80% of which have
counterparts in USNO, 2MASS, and deep FLAMINGOS images. These constitute the
first census of the cluster members with 0.2<~M<~2 Msun. Star locations in
near-infrared color-magnitude diagrams indicate a cluster age around 2 Myr with
a visual extinction of 1<Av<3 at 1.4 kpc, the distance of the Rosette Nebula's
main cluster NGC 2244. We derive the K-band luminosity function and the X-ray
luminosity function of the cluster, which indicate a population ~400-600 stars.
The X-ray-selected sample shows a K-excess disk frequency of 13%. The young
Class II counterparts are aligned in an arc ~3 pc long suggestive of a
triggered formation process induced by the O stars in NGC 2244. The diskless
Class III sources are more dispersed. Several X-ray emitting stars are located
inside the molecular cloud and around gaseous pillars projecting from the
cloud. These stars, together with a previously unreported optical outflow
originating inside the cloud, indicate that star formation is continuing at a
low level and the cluster is still growing. This X-ray view of young stars on
the western side of the Rosette Nebula complements our earlier studies of the
central cluster NGC 2244 and the embedded clusters on the eastern side of the
Nebula. The large scale distribution of the clusters and molecular material is
consistent with a scenario in which the rich central NGC 2244 cluster formed
first, and its expanding HII region triggered the formation of the
now-unobscured clusters RMC XA and NGC 2237. A large swept-up shell material
around the HII region is now in a second phase of collect-and-collapse
fragmentation, leading to the recent formation of subclusters. Other clusters
deeper in the molecular cloud appear unaffected by the Nebula expansion.
