  Upper Scorpius is a subgroup of the nearest OB association,
Scorpius--Centaurus. Its young age makes it an important association to study
star and planet formation. We present parallaxes to 52 low mass stars in Upper
Scorpius, 28 of which have full kinematics. We measure ages of the individual
stars by combining our measured parallaxes with pre-main sequence evolutionary
tracks. We find there is a significant difference in the ages of stars with and
without circumstellar disks. The stars without disks have a mean age of
4.9+/-0.8 Myr and those with disks have an older mean age of 8.2+/-0.9 Myr.
This somewhat counterintuitive result suggests that evolutionary effects in
young stars can dominate their apparent ages. We also attempt to use the 28
stars with full kinematics (i.e.\ proper motion, radial velocity, and parallax)
to trace the stars back in time to their original birthplace to obtain a
trackback age. We find, as expected given large measurement uncertainties on
available radial velocity measurements, that measurement uncertainties alone
cause the group to diverge after a few Myr.
