  We present a measurement of the combined $\nu_e$ + $\bar{\nu}_e$
flux-averaged charged-current inclusive cross section on argon using data from
the MicroBooNE liquid argon time projection chamber (LArTPC) at Fermilab. Using
the off-axis flux from the NuMI beam, MicroBooNE has reconstructed 214
candidate $\nu_e$ + $\bar{\nu}_e$ interactions with an estimated exposure of
2.4$\times10^{20}$ protons on target. Given the estimated purity of 38.6\%,
this implies the observation of 80 $\nu_e$ + $\bar{\nu}_e$ events in argon, the
largest such sample to date. The analysis includes the first demonstration of a
fully automated application of a dE/dx-based particle discrimination technique
of electron and photon induced showers in a LArTPC neutrino detector. We
measure the $\nu_e + \bar{\nu}_e$ flux-averaged charged-current total cross
section to be
${6.84\pm\!1.51~\textrm{(stat.)}\pm\!2.33~\textrm{(sys.)}\!\times\!10^{-39}~\textrm{cm}^{2}/~\textrm{nucleon}}$,
for neutrino energies above 250 MeV and an average neutrino flux energy of 905
MeV when this threshold is applied. The measurement is sensitive to neutrino
events where the final state electron momentum is above 48 MeV/c, includes the
entire angular phase space of the electron, and is in agreement with the
theoretical predictions from \texttt{GENIE} and \texttt{NuWro}. This
measurement is also the first demonstration of electron neutrino reconstruction
in a surface LArTPC in the presence of cosmic ray backgrounds, which will be a
crucial task for surface experiments like those that comprise the
Short-Baseline Neutrino (SBN) Program at Fermilab.
