Atomistic simulations are performed on a series of grain boundary structures in aluminum, and the energies associated with each of their equilibrium configurations are computed. Interatomic potentials using Embedded Atom Method (EAM) are used in conjunction with molecular statics calculations to predict the structure and energy of symmetric tilt grain boundaries (STGB) in aluminum. The width of grain boundaries in these STGB are found to be about 10 . The magnitude of grain boundary energy is proportional to the interplanar spacing normal to grain boundary plane. When grain boundary energies are computed as a function of grain misorientation angle, three low energy configurations (corresponding to three twin structures) are found in the [110] STGB structures. The propensity for grain boundary sliding (GBS) in aluminum is evaluated by computing the energy associated with incremental equilibrium configurations during the sliding process. The number of energy barriers and the magnitude of the individual peaks during GBS vary with different boundary structures. However in all cases, the magnitude of the energy barriers are found to be lower than that of the energy for two free surfaces suggesting that the GBS is more favorable than the formation of grain boundary cleavage under shear loading conditions.