  We present the Multi-Array Galactic Plane Imaging Survey (MAGPIS), which maps
portions of the first Galactic quadrant with an angular resolution, sensitivity
and dynamic range that surpasses existing radio images of the Milky Way by more
than an order of magnitude. The source detection threshold at 20 cm is in the
range 1--2 mJy over the 85% of the survey region (5 deg < l < 32 deg, |b| < 0.8
deg) not covered by bright extended emission. We catalog over 3000 discrete
sources (diameters mostly <30 arcsec) and present an atlas of ~400 diffuse
emission regions. New and archival data at 90 cm for the whole survey area are
also presented. Comparison of our catalogs and images with the MSX mid-infrared
data allow us to provide preliminary discrimination between thermal and
non-thermal sources. We identify 49 high-probability supernova remnant
candidates, increasing by a factor of seven the number of known remnants with
diameters smaller than 5 arcmin in the survey region; several are pulsar wind
nebula candidates and/or very small diameter remnants (D<45 arcsec). We report
the tentative identification of several hundred H II regions based on a
comparison with the mid-IR data; they range in size from unresolved
ultra-compact sources to large complexes of diffuse emission on scales of half
a degree. In several of the latter regions, cospatial nonthermal emission
illustrates the interplay between stellar death and birth. We comment briefly
on plans for followup observations and our extension of the survey; when
complemented by data from ongoing X-ray and mid-IR observations, we expect
MAGPIS to provide the most complete census yet obtained of the birth and death
of massive stars in the Milky Way. Catalogs and images are available on the
MAGPIS web site (http://third.ucllnl.org/gps).
