The first settlers had to haul provisions up the St. Croix River to Grantsburg. One of their daughters died there during the first winter, so they used some of the land as a cemetery. In 1871, Edwin Nelson opened a store in Siren on Little Doctor's Lake, and the post office was moved there when the railroad came through. At the time, potatoes were the main crop. It had a starch factory and a warehouse for potato harvesting.
The population of Grantsburg was 2,464 at the time of the 1865 census. The first county supervisors meeting was held on January 24, 1865, and Michael Jensen, Thore Ingebretson, and Peter Anderson were elected. The town was an important center of trade for the surrounding area and a county seat by 1878. By 1886, the city had a courthouse, school house, several churches, and a number of stores. In 1890, the Northern Pacific railroad completed a branch to Rush City, Minn.
In 1868, many settlers came from the far-off reaches of Minnesota, and made many trips to Grantsburg. Early settlers were driven west to the area by horseback or mules. It took them up to three days to travel round trip. In 1871, a man named Chas. Chipman and his family moved to Grantsburg from southern Minnesota near Granada. They brought their provisions by foot, and even later acquired a team of oxen. In the early days, riding a team of oxen was considered a privilege.