Kitt Peak National Observatory
http://www.noao.edu/kpno/
Supports the most diverse collection of astronomical observatories on Earth.

Apache Point Observatory
http://www.apo.nmsu.edu/
A fairly new facility. There is an on-site search engine.

Golendale Observatory
http://www.perr.com/gosp.html
Near Goldendale, WA. Owned by Washington State and run by the parks dept. It has a 24.5 inch scope.

National Optical Astronomy Observatories Association of Universities for Research in Astronomy (AURA).
http://www.noao.edu/noao.html
A major site for University research, lots of projects. Also, a K-12 outreach program. The site includes an on-line newsletter.

Rattlesnake Mountain Observatory
http://www.aastaonline.org/observatory.html
The facility is located in Southeast Washington between Yakima and the Tri-City area. It has a 31" instrument which is being fitted for remote operation.

Royal Greenwich Observatory British Government.
http://www.rog.nmm.ac.uk/
Founded in 1675 by Charles II. The site includes history, astronomical research, and particle physics research.

Steward Observatory University of Arizona
http://www.as.arizona.edu/
The research division of the University Astronomy Department. One of the premier astronomy research facilities in the world - observational and theoretical. Includes lots of related links such as the famous UofA mirror Lab, and Kitt Peak.

Mount Wilson Observatory
http://www.mtwilson.edu/
The famous facility near Pasadena, CA. Robert Jastrow is the director.