These two national parks are connected and lie north to south across US Rt. 66, US Rt. 40, and the Puerco River in eastern Arizona.

The petrified wood is from trees that lived about 225 million years ago. About 60 million years ago, the Colorado Plateau was pushed up by tectonic forces and exposed to weathering and erosion.

There are more than 600 archeological sites, including Newspaper Rock, an area full of petroglyphs pecked into the dark "desert varnish" patina of the rock to expose lighter hues. There are over 650 glyphs in this area, estimated to be 650 years and older.