We have used scanning tunneling microscopy (STM) to study cleaved Si(111) surfaces. On ordered regions of the 2×1 reconstruction we observe atomic rows with a [2̄11] corrugation amplitude of typically 0.2 Å and an [01̄1] corrugation amplitude of <0.02 Å, consistent with the π-bonded chain model for this surface. Structural disorder is most commonly observed as protrusions along the chains and between chains. A second type of surface disorder is observed in the magnitude and asymmetry of the [2̄11] corrugation amplitude, which we attribute to varying tilts and/or small translations of the π-bonded chains. This latter type of disorder is enhanced in low-voltage images, indicating that the associated defect states have energies concentrated in or near the band gap of 2×1 surface-state energies.