He then served the 18th district in the Minnesota State Senate in 1861, living in Scott County at the time.
On August 15, 1862, he was involved in a confrontation with Mdewakanton tribesmen and his trading partner Andrew Myrick at the Lower Sioux Agency.
Galbraith refused to distribute food on credit, although they were suffering hunger and the government's treaty annuity was late.
Myrick, who made derogatory comments in the incident, was killed on August 18, 1862 while Galbraith managed to escape.
When the hostilities were over he compiled a list of the known Minnesotans casualties both civilian and military.