Field-effect transistors fabricated on graphene grown by chemical vapor deposition (CVD) often exhibit large hysteresis accompanied by low mobility, high positive backgate voltage corresponding to the minimum conductivity point (V min), and high intrinsic carrier concentration (n 0). In this report, we show that the mobility reported to date for CVD graphene devices on SiO2 is limited by trapped water between the graphene and SiO2 substrate, impurities introduced during the transfer process and adsorbates acquired from the ambient. We systematically study the origin of the scattering impurities and report on a process which achieves the highest mobility (μ) reported to date on large-area devices for CVD graphene on SiO2: maximum mobility (μmax) of 7800 cm2/(V·s) measured at room temperature and 12 700 cm2/(V·s) at 77 K. These mobility values are close to those reported for exfoliated graphene on SiO2 and can be obtained through the careful control of device fabrication steps including minimizing resist residue and non-aqueous transfer combined with annealing. It is also observed that CVD graphene is prone to adsorption of atmospheric species, and annealing at elevated temperature in vacuum helps remove these species.