  The scintillation light output response of stilbene crystals has been
measured for protons recoiling along the \textit{a}, \textit{b}, and
\textit{c'} crystalline axes with energies between 1.3 and 10 MeV using
neutrons produced with the tandem Van de Graaff accelerator at Triangle
Universities Nuclear Laboratory. The proton recoil energy and direction were
measured using the coincident detection of neutrons between a stilbene
scintillator and an array of EJ-309 liquid scintillators spanning arranged
neutron recoil angles. The maximum light output was found to coincide with
proton recoils along the \textit{a}-axis, in disagreement with other published
measurements, which reported the \textit{b}-axis as the direction of the
maximum light output. Additional measurements were conducted using two
different stilbene crystals to confirm these results: a second measurement
using the coincident detection of neutrons; measurements of neutron full energy
deposition events along the \textit{a} and \textit{b} axes; and measurements of
the count rate for $^{252}$Cf neutrons traveling along the \textit{a} and
\textit{b} axes directions. All measurements found that recoils along the
\textit{a}-axis produce the maximum light output.
