Yeah the wild thing about the southwest is the open-air museum aspect of it, not the layers on layers. For petroglyphs, the southwest has so many that date to the high middles ages (~1100 AD) you can stumble on them by accident as a hiker. AFAIK the oldest in the area are still thought to be these ones[0], about 9000 years ago. (Always controversial to date rocks I guess, but the oldest North American mummy should be easier and is about the same.[1])

[0] https://en.wikipedia.org/wiki/Winnemucca_Lake [1] https://en.wikipedia.org/wiki/Spirit_Cave_mummy#Dating

The southwest has plenty of layers on layers. Tucson is built on a Spanish fort, which is built on native villages on top of yet older native villages going back almost 4,000 years, as one example.

For another example, most neighborhoods in eastern phoenix are built on top of old Hohokam villages, adjoining older basketmaker sites. The canals throughout the city often follow the old Hohokam canals. Fun fact, the Intel Chandler campus is on top of old hohokam suburbs of Pueblo de los muertos, which is buried under the modern suburbs.

The Puebloan culture in the southwest during that time was basically a full fledged civilization. It's insane how underresearched such a culture is despite having built megastructures like within the Grand Chaco Canyon

did they leave behind significant amounts of writing?

Nope. Which is what makes it so difficult. Additionally, adjacent nations like the Navajo, Apache, and others are very tight lipped about their extremely robust ancestral and oral history because of bad experiences along with taboos.

It felt like a mix of rightful wariness due to untrustworthy opportunistic anthropologists from the 19th and 20th century along with taboos that developed due to some sort of collapse.

Indeed! If you're around Taos, NM, there are several national/state parks that contain the remaining structures of the Pueblans.

The Puye Cliff Dwellings are over 1,000 year olds, and you can free roam most of them. It is quite wild being able to go into cave dwellings in the cliff. I'd highly recommend visiting if anyone is considering it.

I grew up in the bed of a drained lake (https://en.wikipedia.org/wiki/Chicago_Portage#:~:text=this%2...), so there were no native American artifacts to be found. The best we could do were the foundations of some homes that had been on sanitary district land but then torn down with the area reverting to forest (sadly, this forested area which was open to exploration when I was a kid has since been fenced off).

Growing up as a kid, we used to find old wagon wheels and arrow heads frequently. There used to be an old fort not far from where my parent's house was located. A limestone creek ran on the back part of their property and defined the property line. We'd find all sorts of artifacts up and down this creek. I even came across a rock with an circular hole that was obviously bored into it and charring around the hole. I used to have some interesting show-n-tells. This was in the 80s.

Old trade beads can sometimes be found, old stashes and caches. Pony beads, seed beads, and others. They were traded/used as "money". The Hudson's Bay Company brought millions of them to this continent.

https://surface.syr.edu/beads/vol2/iss1/6/