  We examine the reionization history of present-day galaxies by explicitly
tracing the building blocks of halos from the Cosmic Reionization On Computers
project. We track dark matter particles that belong to $z=0$ halos to trace the
neutral fractions at corresponding positions during rapid global reionization.
The resulting particle reionization histories allow us to explore different
definitions of a halo's reionization redshift and to account for the neutral
content of the interstellar medium. Consistent with previous work, we find a
systematic trend of reionization redshift with mass - present day halos with
higher masses have earlier reionization times. Finally, we quantify the spread
of reionization times within each halo, which also has a mass dependence.
