Tidal range is one factor in determining the vertical location of local mean sea level, and it is also a contributor to total water levels and coastal flooding. It is therefore important to understand both the spatial distribution of tidal range and the temporal variation in tidal range, over a wide range of scales. Knowledge of historic tidal range is obtained both through observations and through modeling. This paper reviews numerous observational and modeling studies of historic tidal range variations on decadal to millennial timescales. It also discusses many of the physical processes that are responsible for these variations. Finally, this paper concludes with discussion of several modeling studies that seek to constrain future changes in tidal range in coastal environments.