The United States has 23 UNESCO World Heritage Sites. Of these, ten are cultural, one is mixed, and twelve are natural sites, with most of them being national parks. These sites are places of importance in America's rich cultural history and represent the remarkable diversity of its people. The Mesa Verde National Park and the Yellowstone National Park were the first two American sites to be designated as UNESCO World Heritage Sites in 1978. Since then, a total of 23 sites in 19 states and two territories have been designated. Two sites are transboundary, meaning that they cross the border into Canada. Some of these sites are highlighted below, and a full list of these sites can be found at the bottom of the article.