  The ProtoDUNE-SP detector is a single-phase liquid argon time projection
chamber with an active volume of $7.2\times 6.0\times 6.9$ m$^3$. It is
installed at the CERN Neutrino Platform in a specially-constructed beam that
delivers charged pions, kaons, protons, muons and electrons with momenta in the
range 0.3 GeV$/c$ to 7 GeV/$c$. Beam line instrumentation provides accurate
momentum measurements and particle identification. The ProtoDUNE-SP detector is
a prototype for the first far detector module of the Deep Underground Neutrino
Experiment, and it incorporates full-size components as designed for that
module. This paper describes the beam line, the time projection chamber, the
photon detectors, the cosmic-ray tagger, the signal processing and particle
reconstruction. It presents the first results on ProtoDUNE-SP's performance,
including noise and gain measurements, $dE/dx$ calibration for muons, protons,
pions and electrons, drift electron lifetime measurements, and photon detector
noise, signal sensitivity and time resolution measurements. The measured values
meet or exceed the specifications for the DUNE far detector, in several cases
by large margins. ProtoDUNE-SP's successful operation starting in 2018 and its
production of large samples of high-quality data demonstrate the effectiveness
of the single-phase far detector design.
