Scanning tunneling microscopy is used to confirm the -bonded chain structure of the Si(111)2×1 surface. Both the amplitude and voltage dependence of the vertical corrugation exclude the buckling model for the structure of this surface. Spectroscopic measurements of the tunneling current versus voltage identify a band gap for the 2×1 surface states. Spatial images of disorder-related states are obtained by tunneling at energies inside of this band gap. © 1986 The American Physical Society.