Magnetic-field driven insulating states in graphene are associated with samples of very high quality. Here this state is shown to exist in monolayer graphene grown by chemical vapor deposition (CVD) and wet transferred on Al2O3 without encapsulation with hexagonal boron nitride (h-BN) or other specialized fabrication techniques associated with superior devices. Two-terminal measurements are performed at low temperature using a GaAs-based multiplexer. During high-throughput testing, insulating properties are found in a graphene device 10 μm long, 10 μm wide at one contact, with a ~440 nm wide constriction at the other. The low magnetic field mobility ~6000 cm^2 V^-1 s^-1. An energy gap induced by magnetic field opens at charge neutrality, leading to diverging resistance and current switching of order 104 with DC bias voltage at an approximate electric field strength 0:04 V m􀀀1 and high magnetic field. DC source–drain bias measurements show behavior associated with tunneling through a potential barrier and a transition between direct tunneling at low bias to Fowler-Nordheim tunneling at high bias, from which the tunneling region is estimated to be of order ~100 nm. Transport becomes activated with temperature, from which the gap size is estimated to be 2.4 to 2.8 meV at B = 10 T. Results suggest that a local electronically high quality region exists within the constriction which dominates transport at high B, causing the device to become insulating and act as a tunnel junction. The use of wet transfer fabrication techniques of CVD material without encapsulation with h-BN and combined with multiplexing illustrates the convenience of these scalable and reasonably simple methods to find high quality devices for fundamental physics research, and with functional properties.