  The dynamical states of molecular clouds may affect the properties of the
stars they form. In the vicinity of the Trifid Nebula ($d=1180\pm25$ pc), the
main star cluster (Trifid Main) lies within an expanding section of the
molecular cloud; however, ~0.3 deg to the north (Trifid North), the cloud's
velocity structure is more tranquil. We acquired a Chandra X-ray observation to
identify pre-main-sequence stars in Trifid North, complementing a previous
observation of Trifid Main. In Trifid North, we identified 51 candidate
pre-main-sequence stars, of which 13 are high-confidence Trifid members based
on Gaia EDR3 parallaxes and proper motions. We also re-analyzed membership of
Trifid Main and separated out multiple background stellar associations. Trifid
North represents a stellar population ~10% as rich as Trifid Main that formed
in a separate part of the cloud. The 1D stellar velocity dispersion in Trifid
North ($0.6\pm0.2$ km/s) is three times lower than in Trifid Main ($1.9\pm0.2$
km/s). Furthermore, in Trifid Main, proper motions indicate that the portion of
the star cluster superimposed on the optical nebula is expanding. Expansion of
the HII region around the O-star HD 164492A, and the resulting gas expulsion,
can explain both the motions of the stars and gas in Trifid Main. Contrary to
previous studies, we find no evidence that a cloud-cloud collision triggered
star formation in the region.
