The ultrahigh vacuum scanning tunneling microscope (UHV-STM) is used to investigate the electrical and structural properties of single-walled carbon nanotubes (SWNTs) supported on both clean and hydrogen-terminated Si(100) surfaces. Dry contact transfer (DCT) of SWNTs in situ precludes contamination of the SWNT/Si interface and enables sensitive atomic-scale measurements. Tunneling current-voltage (I-V) and conductance-voltage (dI/dV-V) spectra have been acquired from both semiconducting and metallic SWNTs. The compatibility of SWNTs with STM nanofabrication on the Si(100)-2×1:H surface is exemplified by the integration of H-resist nanolithography with adsorbed SWNTs. Contrary to earlier UHV-STM studies of SWNTs on Au(111), the motivation for our work is derived from the technological importance of the Si(100) substrate and the development of hybrid SWNT-Si nanoelectronic devices.