  The Next-Generation Very Large Array (ngVLA) will be critical for
understanding how galaxies are built and evolve at the earliest epochs. The
sensitivity and frequency coverage will allow for the detection of cold gas and
dust in `normal' distant galaxies, including the low-J transitions of molecular
gas tracers such as CO, HNC, and HCO+; synchrotron and free-free continuum
emission; and even the exciting possibility of thermal dust emission at the
highest (z~7) redshifts. In particular, by enabling the total molecular gas
reservoirs to be traced to unprecedented sensitivities across a huge range of
epochs simultaneously -- something no other radio or submillimeter facility
will be capable of -- the detection of the crucial low-J transitions of CO in a
diverse body of galaxies will be the cornerstone of ngVLA's contribution to
high-redshift galaxy evolution science. The ultra-wide bandwidths will allow a
complete sampling of radio SEDs, as well as the detection of emission lines
necessary for spectroscopic confirmation of elusive dusty starbursts. The ngVLA
will also deliver unique contributions to our understanding of cosmic magnetism
and to science accessible through microwave polarimetry. Finally, the superb
angular resolution will move the field beyond detection experiments and allow
detailed studies of the morphology and dynamics of these systems, including
dynamical modeling of disks/mergers, determining the properties of outflows,
measuring black hole masses from gas disks, and resolving multiple AGN nuclei.
We explore the contribution of a ngVLA to these areas and more, as well as
synergies with current and upcoming facilities including ALMA, SKA, large
single-dish submillimeter observatories, GMT/TMT, and JWST.
