At "the broken bridge site", researchers used radiocarbon dating of artifacts to determine it was inhabited about 3280 BCE, the oldest human-inhabited site in the valley.
 They consider it part of Skaggs Phase (3000 BCE—500 BCE).

"Oregon Oak Place" was dated at 1843 BCE.
The surveyors suggested that, compared to the lower river valleys, this remote area was more sparsely settled before the Pomo people arrived.

Both of these Skaggs Phase-sites contained millstones and handstones for grinding seeds.
 The villages may have been used for hunting or temporary camps.
Obsidian was used rarely, and it came from Mt. Konocti in present-day Lake County.
 There were no petroglyphs.
 The population lived only along major creeks.

"The Dry Creek Phase" lasted from 500 BCE to 1300 CE.
 During this phase, the indigenous people settled the lands more extensively and permanently.
 Archaeologists believe a Pomo group took over the lands from the earlier peoples in this phase.
 They created 14 additional sites in the Warm Springs and Upper Dry Creek areas.
 Bowl mortars and pestles appeared in this phase, probably used by women to pound acorns (as opposed to the milling stones used for seeds).
The sites were more permanent and lifeways "more complex".
 Decorative beads and ornaments were made in this phase, and half the artifacts were made of obsidian.
 Steatite or soapstone objects were found, which must have been imported into the region through trade, as the rock does not exist locally.
 Relatively soft and easy to carve, soapstone was used to make beads, pendants and mortars.
 Trade was on a large scale beyond the region.
 The largest and only substantial steatite mine in California existed on Catalina Island, one of the Channel Islands off the coast of what is now Los Angeles.
The existence of steatite in Pomo and Northern California native sites is a strong indicator of the size and complexity of native California trade networks.

The next phase, named the "Smith Phase" after the Pomo consultants, lasted from 1300 CE to the mid-19th century.
 Researchers mapped 30 sites in this era showing a gradual transition and intensification of trends.
 The bow and arrow appeared as the main technological advancement.
 Manufacturing of shell beads, with accompanying production of drills to make holes for stringing and sewing, was important.
 Drills were found in high numbers.
 Numerous clamshell beads, a major currency among the Indians of Central California, were also found, indicating a vast trade network.
At "the broken bridge site", researchers used radiocarbon dating of artifacts to determine it was inhabited about 3280 BCE, the oldest human-inhabited site in the valley.  They consider it part of Skaggs Phase (3000 BCE—500 BCE).
"Oregon Oak Place" was dated at 1843 BCE. The surveyors suggested that, compared to the lower river valleys, this remote area was more sparsely settled before the Pomo people arrived.
Both of these Skaggs Phase-sites contained millstones and handstones for grinding seeds.  The villages may have been used for hunting or temporary camps. Obsidian was used rarely, and it came from Mt. Konocti in present-day Lake County.  There were no petroglyphs.  The population lived only along major creeks.
"The Dry Creek Phase" lasted from 500 BCE to 1300 CE.  During this phase, the indigenous people settled the lands more extensively and permanently.  Archaeologists believe a Pomo group took over the lands from the earlier peoples in this phase.  They created 14 additional sites in the Warm Springs and Upper Dry Creek areas.  Bowl mortars and pestles appeared in this phase, probably used by women to pound acorns (as opposed to the milling stones used for seeds). The sites were more permanent and lifeways "more complex".  Decorative beads and ornaments were made in this phase, and half the artifacts were made of obsidian.  Steatite or soapstone objects were found, which must have been imported into the region through trade, as the rock does not exist locally.  Relatively soft and easy to carve, soapstone was used to make beads, pendants and mortars.  Trade was on a large scale beyond the region.  The largest and only substantial steatite mine in California existed on Catalina Island, one of the Channel Islands off the coast of what is now Los Angeles. The existence of steatite in Pomo and Northern California native sites is a strong indicator of the size and complexity of native California trade networks.
The next phase, named the "Smith Phase" after the Pomo consultants, lasted from 1300 CE to the mid-19th century.  Researchers mapped 30 sites in this era showing a gradual transition and intensification of trends.  The bow and arrow appeared as the main technological advancement.  Manufacturing of shell beads, with accompanying production of drills to make holes for stringing and sewing, was important.  Drills were found in high numbers.  Numerous clamshell beads, a major currency among the Indians of Central California, were also found, indicating a vast trade network.
Pomo