Keet Seel is a Navajo term meaning "Broken pottery scattered around."
The people started building the cliff dwelling around 1250 CE but between 1272 and 1275 there was a sudden building spurt. Then construction slowed down until it stopped completely in 1286. Within 20 years the pueblo was completely abandoned, until the Navajo stumbled over it more than 300 years later.
The ruins of Keet Seel were so well protected by the canyon wall it was built into that the pueblo is among the best preserved of all ancient constructions in North America. At its height, there were more than 150 rooms built, including some that were just for storing grain. There were also six kivas. Apparently, the local environment was good enough to support a relatively large population and provide them with food surpluses. That said, the peak population around 150 people may have also contributed to the abandonment as the climate continued to get more dry up to about 1300 CE (not that they would have known anything about that arbitrary number).
Keet Seel is located within the archaeological area known as "Kayenta-Tusayan." Today it is part of "Navajo National Monument." Interesting as none of the three non-contiguous pieces of that Monument have anything to do with the Navajo people. They were all abandoned long before the Navajos arrived in the area. And another note: the Navajo had left the ruins alone and removed nothing during the centuries that they knew about them. The first Euro-Americans to find them began removing artifacts and selling them almost immediately.
Archaeologists have proposed reasons for the abandonment based on changes in weather patterns. The Hopis tell a story more of a spiritual quest concerning the Snake and the Horn clans. In the Hopi story, the Horn clan forced the Snake clan out because the Snake clan children were biting other children and causing them to die. The story is likely an allegory for an actual historical event: as the climate got more dry rattlesnakes probably became more of a problem. In this case, members of the Snake clan probably relocated to the Hopi mesas as there were members of Snake clans in each of the pueblos there. I haven't come across a record of Horn clan migrants arriving at the Hopi mesas in the same time period, although there have been Horn clan representatives in most of the Hopi pueblos almost since the beginning. But Keet Seel and Betatakin were both competely abandoned before 1320 CE.