Historical and archaeological evidence points to the Navajo people entering the Southwest around 1400 AD. At least that's what the found archaeological evidence points at. However, as a nomadic group, they wouldn't have left much hard material behind as they moved around and archaeology in the Southwest mostly hovers around hard materials: tools, bones, ruins, pottery. Judging from the impact on the societies around them, dates would better be determined by extrapolating from there. It wasn't any "Great Drought" that forced the people down from their canyons in southwest Colorado, it was more likely incoming warlike Athapaskan people. Over time the newcomers separated into what is now the Apache, Navajo, Comanche and Kiowa tribes.
Navajo oral history still contains stories of that migration as the journey began in eastern Alaska and northwestern Canada centuries after their ancestors made the journey across the Bering Land Bridge from central Asia, around 13,500 years ago. They were primarily hunter-gatherers until they came into contact with the Pueblo peoples and learned the basics of how to survive in this significantly drier climate. Navajo oral history points to a long relationship between the Navajos and the Puebloans as they learned from and traded with each other. The problem with oral history is it records events and seasons, not years, decades or centuries.
When the Spanish first arrived, the Navajos occupied much of the area between the San Francisco Peaks (in Arizona), Hesperus Mountain and Blanca Peak (in Colorado) and Mount Taylor (in New Mexico). Spanish records indicate the Navajo traded bison meat, hides and stone to the Puebloans in exchange for maize and woven cotton goods. It was the Spanish who brought sheep to the New World and the Navajo took to sheep-herding quickly. Sheep became a form of currency and sign of wealth.
When the Americans arrived in force after 1846, things began to change. The first fifteen years were marked by broken promises and treaties by the Americans, leading to increasing raids by the Navajo and animosities on both sides. Finally, Brigadier General James H. Carleton ordered Colonel Kit Carson to round up the Navajo and transport them to Bosque Redondo in eastern New Mexico for internment. Carson succeeded only by engaging in a scorched earth campaign in which his troops swept through Navajo country killing anyone carrying a weapon and destroying any crops, livestock and dwellings they found. Facing starvation and death, the last band of Navajos surrendered at Canyon de Chelly in 1864.
Prior to this, Carson had been a welcome and respected friend for most Native Americans. The methods used against the Navajo pretty much destroyed that reputation and he became known as an "Indian killer." After the hostilities of the Civil War ceased, Carson went to the Fort Lyon area in Colorado where he was an appointed Indian Agent for the Southern Arapahoe and Cheyenne. He died a few years later, six months after his beloved wife passed on.
Carson's campaign in 1864 led straight into "the Long Walk" to Bosque Redondo, a 300-mile trek during which at least 10% of the tribe died along the way. At Bosque Redondo they discovered the government had not allocated an adequate supply of water, livestock, provisions or firewood to support the 4,000-5,000 people being interned there. They also discovered on arrival that the government had also interned people from another tribe there, deadly enemies of the Navajo. The Army also did little to protect the Navajo from raids by other tribes or by local Anglo citizens. Another 10% of the Navajo Nation died there and those still alive in 1868 almost wished they'd died, too.
The failure was such that the Federal government and the Navajo negotiated a treaty that allowed the people to walk back to a reservation that was only a shadow of their former territory little more than a couple years after they had been forced out. However, the years since have seen additions to the reservation until today it is the largest Native American Reservation in the 48 contiguous states.
Large deposits of uranium ore were discovered on the Navajo Nation after World War II but the mining that followed ignored basic environmental protection for the workers, the waterways and the land. The Navajo have made claims of high rates of cancer and lung disease from the environmental contamination but the Federal government has yet to offer comprehensive compensation. What compensation has been offered has been held up by a Congress seemingly intent on waiting for those workers to die.
As a semi-nomadic tribe, the Navajo never made much pottery, preferring to use baskets for most storage purposes. After learning how to make pottery from the Puebloans of the Rio Grande area, they did produce a small amount of pottery for ceremonial uses. Once they were more settled, pottery began to make more sense. Through the 1700's and into the mid 1800's, there was a significant amount of pottery produced for sale to local settlers but once the railroads came through and trading posts were set up, it was much easier to purchase enameled cookware and such, so Navajo pottery making almost completely died out.
Because of their geographical location, those few Navajo potters producing pottery for either ceremonial or personal use were never approached by the railroad traders. Like today, most of the remaining Navajo potters were located in the environs of Black Mesa as that was where the best clay was to be found.
Rose Williams is considered the matriarch of modern Navajo pottery. She learned from Grace Barlow (her aunt) and passed her knowledge and experience on to her daughters and many others. Today, most Navajo pottery is heavy, thick-walled and coated with pine pitch (a sealer they also use on many of their baskets).
Much Navajo pottery has little in the way of design but many pieces have a repousse biyo' (a traditional decorative fillet below the rim). Because of tribal religious restrictions, many traditional Navajo potters either don't add any decorations to their pieces or they stick to pre-approved Navajo weaving patterns. Those Navajo potters who have become "Christianized" ignore those religious restrictions (and there are multiple splinter Christian missionary groups operating all over the Navajo Nation).