  The UCNA experiment was designed to measure the neutron $\beta$-asymmetry
parameter $A_0$ using polarized ultracold neutrons (UCN). UCN produced via
downscattering in solid deuterium were polarized via transport through a 7 T
magnetic field, and then directed to a 1 T solenoidal electron spectrometer,
where the decay electrons were detected in electron detector packages located
on the two ends of the spectrometer. A value for $A_0$ was then extracted from
the asymmetry in the numbers of counts in the two detector packages. We
summarize all of the results from the UCNA experiment, obtained during run
periods in 2007, 2008--2009, 2010, and 2011--2013, which ultimately culminated
in a 0.67\% precision result for $A_0$.
