Verification and validation are key components to performing a quality computational fluid dynamics (CFD) analysis. When referring to verification, this traditionally implies a grid independence study to ensure the CFD results are accurate with respect to the mesh sizing. However, this study explores why a comprehensive verification study is necessary to evaluate the influence of the flow domain size. The drag coefficient was used as the basis to compare different flow domains. Due to flow around a rectangular cylinder near a plane wall boundary, it was found there are three main effects present that influence the domain sizing in each coordinate direction. An insufficient vertical domain leads to suppressed streamlines which locally accelerate the flow and artificially increases the drag coefficient. An adequate horizontal domain length upstream from the cylinder allows the stagnation pressure on the rectangular cylinder to propagate unimpeded to the flow inlet. A sufficient horizontal domain length downstream from the cylinder allows the flow wake to completely develop before exiting the outlet. Through appropriately sizing the CFD domain, a comprehensive verification study leads to accurate and useful results.