  Following the Pluto fly-by of the New Horizons spacecraft, the mission
provided a unique opportunity to explore the Kuiper Belt in-situ. The
possibility existed to fly-by a Kuiper Belt object (KBO) as well as to observe
additional objects at distances closer than are feasible from earth-orbit
facilities. However, at the time of launch no KBOs were known about that were
accessible by the spacecraft. In this paper we present the results of 10 years
of observations and three uniquely dedicated efforts -- two ground-based using
the Subaru Suprime Camera, the Magellan MegaCam and IMACS Cameras, and one with
the Hubble Space Telescope -- to find such KBOs for study. In this paper we
overview the search criteria and strategies employed in our work and detail the
analysis efforts to locate and track faint objects in the galactic plane. We
also present a summary of all of the KBOs that were discovered as part of our
efforts and how spacecraft targetability was assessed, including a detailed
description of our astrometric analysis which included development of an
extensive secondary calibration network. Overall, these efforts resulted in the
discovery of 89 KBOs including 11 which became objects for distant observation
by New Horizons and (486958) Arrokoth which became the first post-Pluto fly-by
destination.
