Past research regarding historical trauma in the Lakota, one of the three major groups of the Oceti Sakowin or Sioux, has contributed to the historical trauma theory, but gaps continue to exist. The purpose of the study was to examine the historical trauma experiences and grief responses of individuals who identify as Oceti Sakowin, specifically the Nakota and Dakota, including present experiences. Interpretive phenomenological analysis was the study's methodology and the conceptual framework of this research was historical trauma theory, which refers to the persistence of trauma and transmission of trauma from generation to generation. Participant interviews were conducted using a researcher-designed interview schedule. Participants were Oceti Sakowin who identify as Nakota or Dakota and who were over the age of 18, and a total of 8 participants were interviewed. This research yielded themes about how the phenomena affected the participants, which can provide insight into how others who have had their own experiences relate to the phenomena. These themes were concerns and pain about ancestors' experience, concern for personal experiences but hope for the future, and the loss of the past is the sorrow of today. Increasing the knowledge of historical trauma and historical trauma grief responses can lead to better understanding that leads to positive social change through greater empathy and sensitivity toward those who have had these experiences, which can increase respect toward the traditions and cultures of others as well as culturally informed interventions to address historical trauma and grief.