  We present an overview and description of the eMERLIN Galaxy Evolution survey
(eMERGE) Data Release 1 (DR1), a large program of high-resolution 1.5 GHz radio
observations of the GOODS-N field comprising $\sim140$ hours of observations
with eMERLIN and $\sim40$ hours with the Very Large Array (VLA). We combine the
long baselines of eMERLIN (providing high angular resolution) with the
relatively closely-packed antennas of the VLA (providing excellent surface
brightness sensitivity) to produce a deep 1.5 GHz radio survey with the
sensitivity ($\sim 1.5\mu$Jy beam$^{-1}$), angular resolution ($0.2"$--$0.7"$)
and field-of-view ($\sim15' \times 15'$) to detect and spatially resolve
star-forming galaxies and AGN at $z\gtrsim 1$. The goal of eMERGE is to provide
new constraints on the deep, sub-arcsecond radio sky which will be surveyed by
SKA1-mid. In this initial publication, we discuss our data analysis techniques,
including steps taken to model in-beam source variability over a $\sim20$ year
baseline and the development of new point spread function/primary beam models
to seamlessly merge eMERLIN and VLA data in the $uv$ plane. We present early
science results, including measurements of the luminosities and/or linear sizes
of $\sim500$ galaxes selected at 1.5 GHz. In combination with deep Hubble Space
Telescope observations, we measure a mean radio-to-optical size ratio of
$r_{\rm eMERGE}/r_{\rm HST}\sim1.02\pm0.03$, suggesting that in most
high-redshift galaxies, the $\sim$GHz continuum emission traces the stellar
light seen in optical imaging. This is the first in a series of papers which
will explore the $\sim$kpc-scale radio properties of star-forming galaxies and
AGN in the GOODS-N field observed by eMERGE DR1.
