The Pueblo I Era, from CE 750 to 900, is the first period in which Ancient Pueblo People begin living in pueblo structures and realize an evolution in architecture, artistic expression, and water conservation.

Pueblo I, a Pecos Classification, is similar to the early "Developmental Pueblo Period" of CE 750 to 1100.

People construct and live in pueblos, which are surface level, flat-roofed homes.

At the beginning of the period pueblos are made with jacal construction.

Wooden posts are used to create a frame to supported woven material and a covering of mud.

Later in the period, stone slabs will sometimes used around the dwelling foundation.

The pueblos are made of several rooms that form a straight row or in a crescent shape.

Sometimes they build the dwellings two rows thick with a combination of living rooms with fire pits and storage rooms.

The Pueblo I villages are larger than the settlements of the preceding Basket Maker period; In the Four Corners region the average of five to ten pit-house per settlement rises to twenty to thirty pit-houses per community.

In some cases, the Pueblo I communities are quite large.

Southeastern Utah's Alkali Ridge has about one hundred and thirty rooms built on the surface, with sixteen pit-houses and two kivas.