We carried out scanning tunneling spectroscopy measurements on exfoliated monolayer graphene on SiO2 to probe the correlation between its electronic and structural properties. Maps of the local density of states are characterized by electron and hole puddles that arise due to long-range intravalley scattering from intrinsic ripples in graphene and random-charged impurities. At low energy, we observe short-range intervalley scattering which we attribute to lattice defects. Our results demonstrate that the electronic properties of graphene are influenced by intrinsic ripples, defects, and the underlying SiO2 substrate.