Obviously Great Plains tribes would be aware of other Great Plains tribes and maybe a few Ohio Valley tribes, but how far does that go? Is there any evidence that say a Sioux might have run into an Inuit on random travels? Were Native Americans explorers/interminglers at all? I've been reading some papers in my college class and they're all very superficial histories about occasional border skirmishes between neighboring tribes.
TL;DR: Did Native American societies mix/travel peacefully at all and if so, to what extent?
There's always room for discussion, but perhaps the section Pre-Columbian Trade and Contact in our FAQ will answer your inquiry.
Did Native American societies mix/travel peacefully at all and if so, to what extent?
As you'll have noticed in the Pre-Columbian Trade and Contact section of the FAQs, there's a long history of peaceful interactions between American nations. I've already written quite a bit on the topic in the FAQ links, so I'll just hit some quick highlights to facilitate additional conversation here:
Between 1700 BCE and 700 BCE, Poverty Point in northeastern Louisiana was the the largest (known) city in what's now the US, with a population of around 5,000 and counting (as we continue to find additional residential areas around the main complex). Poverty Point was the epicenter of a large trading network, drawing in resources from at least as far way as Lake Superior. Going to other way, artifacts associated with Poverty Point itself have been found as far north as the Ohio River in Indiana.
Between 1000 BCE and 400 CE (more or less), the Ohio Valley was another major epicenter of trade, first among the Adena culture(s) and then later among the Scioto (Ohio) Hopewell - the most prominent of the various Hopewell cultures of the era. The trade routes of the Scioto Hopewell brought in copper from Lake Superior, silver from northern Ontario, marine resources from the Atlantic and the Gulf of Mexico, bear claws and obsidian from the Rockies and beyond. Hopewellian artists also depict exotic animals like jaguars, ocelots, and bighorn sheep that don't live in their own territory, indicating that they saw these animals in their travels.
Between 1000 CE to European contact and beyond, the various Mississippian nations also had extensive trade networks. When de Soto marched through the Southeast, he captured a young man named Perico in northern Florida. Perico was actually a trader who had come down from Cofitachequi, a large Mississippian nation based in South Carolina. Perico became a guide and translator for de Soto as the entrada marched among the Muskogean speaking peoples of the Southeast (working alongside Juan Ortiz, a Spanish sailor who had been stranded in central Florida for years and learned the local Timucuan language before teaming up with de Soto). As de Soto's entrada snaked its way from nation to nation, it would encountered other evidence of trade, including exotic goods from more distant lands to the traders themselves. Of note here would be the presence of cotton and turquoise in the lower Mississippi, both of which came from Pueblo communities in New Mexico. In exchange, the Pueblo received the highly prized Osage bows and yaupon tea (the famous "Black Drink") that came out of southern Mississippian region.
The French historian du Pratz, in his History of Louisiana, recounts the travels of the Moncacht-ape, who journeyed from one end of the continent to the other sometime before the 1720s (when du Pratz interviewed him). This one is different from the other trade focused examples because it's explicitly about a man who decided one day to hit the road and see what he could learn along the way. Since he talks about needing to avoid the Haudenosaunee (Iroquois), it sounds like this journey would have taken place prior to the Great Peace of 1701. Of course, there's some debate over whether this journey took place at all, but I find the argument against it unconvincing.
This map shows the trade routes in the western part of the what's now the US, based on pre-1700s information (for example, note that the Comanche are still in Wyoming, the Lakota (Teton) are still east of the Missouri, and La Junta is still a significant trading site). Unfortunately, I don't have a convenient map that shows the same information for the east, but instead we have maps of the specific trail systems used during the colonial period: Northern New England, Southern New England, New York, Pennsylvania, Ohio, the Southeast. Among the most important of these are the two Great Paths - the north-south Great Path ran from Niagara Falls, down the central valleys of the Appalachian (if you look at the Southeast map, you can see it extending north out of Virginia), and terminated at the Mobile Bay; the east-west Great Path ran the mouth of the Susquehanna River, westward through Pennsylvania and Ohio, where it turned northwest to Detroit, hopped across the Straits of Mackinac into the Upper Peninsula before turning west again toward the Plains - and the Scioto Trail which ran from the mouth of the Sandusky River on Lake Erie (where it intersected the east-west Great Path), southward along the Scioto River, across the Ohio into Kentucky and from more or less straight south to Mobile Bay (where it intersected the north-south Great Path). These three are all likely very old paths going back some 2000 years or more, though some specific local features may have shifted slightly over the years.
