Hello Cathy,
There are indeed many sites in the U.S. that are considered to be associated with observations of the Sun. We have a site in Cahokia, Illinois called Woodhenge, for instance (see http://solarscience.msfc.nasa.gov/suntime/slshow3.stm#cahokia and http://www.utexas.edu/courses/wilson/ant304/biography/arybios98/mcbridebio.html). There's also the Big Horn Medicine Wheel in Wyoming (http://solar-center.stanford.edu/AO/bighorn.html). In the southeast, there are many Indian "mounds," some of which may have been used for solar observations; these include Ocmulgee and Etowah in Georgia and Moundville in Alabama (see http://www.lostworlds.org/etowah_mounds.html). There were also mounds at Cahokia.