More petroglyphs and pictographs (Rock Art) per square mile that just about anywhere in the USA.
Petroglyph National Park - Amazing Rock Art - Petroglyph National Monument has one of the biggest, and easiest to find group of petroglyphs in the United States. There are over 20,000 carvings in this monument. It is on the western side of Albuquerque, New Mexico, and is easy to reach. The vast majority of the petroglyphs (rock carvings) are from the Pueblo IV period. That runs from about 1300 to 1650 (AD or CE, as you prefer). A few are up to 1,000 years old. A tiny amount were done by Spanish settlers when this was still part of Spain or Mexico. I visited the park on April 12, 2016.
There are several hiking trails in the Park. Here is some basic info for each:
Boca Negra Canyon: 1 mile long, 1 hour time - 100 petroglyphs
Rinconada Canyon: 2.2 miles, 1.5 hours time - 300 petroglyphs
Piedras Marcadas Canyon: 1.5 miles, 1 hour plus - 400 petroglyphs
My personal video of the area is below.