I am making my first ever trip to the United States next March/April (2010). After arriving I will be spending 10 days in and around Los Angeles and then heading off for a three week road trip, travelling in a huge anticlockwise circle.

My plan is CA>NV>UT>AZ>NM>TX>OK>KS>NE>SD>WY>MT>ID and back to CA. I will not have time to get east of the Missouri River - another trip perhaps I need to average 300-400km each day.

Obviously there is a huge list of natural places I want to see and photograph. I would love to hear your suggestions (particularly from those of you in the US) of "not to be missed" locations. As I will be travelling with my wife and two children I will not always be able to be at some locations at the ideal time of day (sunrise or sunset) so I will have to make do with what I find to be able to keep on schedule.

Your suggestions please?