  The North Celestial Pole Loop (NCPL) provides a unique laboratory for
studying the early stages of star formation, in particular the condensation of
the neutral interstellar medium (ISM). Understanding the physical properties
that control the evolution of its contents is key to uncovering the origin of
the NCPL. Archival data from the NCPL region of the GHIGLS 21 cm line survey
(9'4) are used to map its multiphase content with ${\tt ROHSA}$, a Gaussian
decomposition tool that includes spatial regularization. Column density and
mass fraction maps of each phase were extracted along with their uncertainties.
Archival data from the DHIGLS 21 cm (1') survey are used to further probe the
multiphase content of the NCPL. We have identified four spatially (and
dynamically) coherent components in the NCPL, one of which is a remarkably
well-defined arch moving at about $14\ {\rm km s^{-1}}$ away from us that could
be a relic of the large-scale organized dynamical process at the origin of the
phase transition. The cold and lukewarm phases together dominate the mass
content of the neutral gas along the loop. Using absorption measurements, we
find that the cold phase exhibits slightly supersonic turbulence.
