The electrical resistivities of copper films sputtered in either argon or an argon-hydrogen atmosphere are measured in real time, during growth. The electrical resistivities for both cases are observed to be functions of the film's thickness, with the films grown in the hydrogen containing atmosphere possessing a resistivity of 4.5 +/- 0.2 μΩ-cm at 40 nm, lower than the resistivity of 5.0 +/-0.3 μΩ-cm for 40 nm thick films grown in the argon atmosphere. Furthermore, the electrical resistivities for both sets of films were observed to continue to evolve after the termination of deposition. The amount of change and the rate of change were observed to depend on the film's thickness as well as atmosphere the films were grown in. Measurements made by X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate that the presence of hydrogen also influences the preferential crystallographic orientation as well as grain size distribution. These measurements indicate that the differences in the microstructure are correlated to the observed differences in the behavior of the electrical resistivities.