Before the arrival of Europeans and Russians, the wide valley containing Santa Rosa was home to a strong and populous tribe of Pomo natives known as the Bitakomtara. The Bitakomtara controlled the valley closely, barring passage to others until permission was arranged. Those who entered without permission were subject to harsh penalties. The tribe gathered at ceremonial times on Santa Rosa Creek near present-day Spring Lake Regional Park. Upon the arrival of Europeans, the Pomos were decimated by smallpox brought unintentionally from Europe, and by the eradication efforts of Anglo settlers. By 1900 the Pomos had been reduced by 95%.