This dissertation is inspired by recent progress in the chemistry, physics, and nanotechnology of graphene, a single atomic layer of carbon atoms. This all-surface material is easily influenced by its physical and chemical environment. Studying and controllably modifying the electrical properties of graphene while minimizing damage to the lattice continues to be a challenge to the scientific and engineering community. This thesis defense focuses on the covalent attachment of molecules with different functional groups to graphene and how functionalization modifies the electrical transport properties of graphene field effect transistor devices. Covalent functionalization is shown to predominantly induce p-type doping, undiminished mobility, and higher conductivity at the neutrality point. Physisorbed molecules desorb easily and do not have a significant effect on the electronic properties of graphene devices. Statistical analysis of multiple devices enables us to extract trends even though identically fabricated graphene devices can exhibit a wide range of electrical behaviors, emphasizing that conclusions should not be drawn based on singular extremes. We will briefly discuss defect-minimalized graphene antidot lattices produced by placing graphene on pre-patterned substrates, Raman mapping of graphene devices with multiple neutrality points, graphene growth from solid carbon sources, hexagonal graphene onions, and graphene resistor devices that are currently being exposed to radiation aboard the International Space Station. Overall, the work accomplished in this dissertation constitutes a step forward toward controllable device behavior in graphene based electronics.