Ridges are observed on epitaxial graphene on 6H-SiC(0001) by scanning tunneling microscopy (STM). Atomic resolution imaging reveals that they are in fact bulged regions of the graphene layer, occurring as a result of bending and buckling to relieve the compressive strain. Furthermore, their length, direction, and distribution can be manipulated, and new ones can even be created by the tip-surface interactions during STM imaging. The lower limit of terrace size for ridge formation is estimated to be approximately 80 nm, and nearly ridge-free graphene film can be obtained on vicinal 3.5 degrees miscut substrates.