  The counting rate of single muon tracks from the Project GRAND proportional
wire chamber array is examined during the Ground Level Event (GLE) of April 15,
2001. The GLE was seen by neutron monitor stations shortly after the time of
the solar X-ray flare. GRAND's single muon data are presented and compared with
neutron monitor data from Climax, Newark, and Oulu. The single muon data have
mean primary hadron energies higher than those of these neutron monitor
stations and so contain information about higher energy hadrons. For the single
muon data for Project GRAND, the GLE is detected at a statistical significance
of 6.1-sigma.
