  We report here results from a Chandra ACIS observation of the stellar
populations in and around the Messier 17 H II region. The field reveals 886
sources, 771 of which have stellar counterparts in infrared images. In addition
to comprehensive tables of X-ray source properties, several results are
presented: * The X-ray Luminosity Function is calibrated to that of the Orion
Nebula Cluster population to infer a total population of roughly 8000--10,000
stars * About 40% of the ACIS sources are heavily obscured with A_V > 10 mag.
Some are concentrated around well-studied star-forming regions but most are
distributed across the field. X-ray emission is detected from 64 of the
hundreds of Class I protostar candidates that can be identified by near- and
mid-infrared colors. These constitute the most likely protostar candidates
known in M17. * The spatial distribution of X-ray stars is complex: we find a
new embedded cluster, a 2 pc-long arc of young stars along the southwest edge
of the M17 H II region, and 0.1 pc substructure within various populations.
These structures may indicate that the populations are dynamically young. * All
(14/14) of the known O stars but only about half (19/34) of the known B0--B3
stars in the M17 field are detected. Six of these stars exhibit very hard
thermal plasma components (kT>4 keV) that may be due to colliding wind
binaries. More than 100 candidate new OB stars are found, including 28 X-ray
detected intermediate- and high-mass protostar candidates with infrared
excesses. * Only a small fraction (perhaps 10%) of X-ray selected high- and
intermediate- mass stars exhibit K-band emitting protoplanetary disks,
providing further evidence that inner disks evolve very rapidly around more
massive stars.
