In 1776, as America ghained her independence, Polk County was a small part of the great Northwest Territory formed in 1763 when France ceded this area to Great Britain.

The region was inhabited by the Chippewa Indians, but as early as 1681 the first white men had visited the area. Daniel Greysolon De Duhlut, with five French Canadians, came down the st. Croix River and traded with the native Americans. Father Louis Hennepin also visited here about 1681.

The Northwest Territory came under the jurisdiction of the United States because of the victory of George Rogers Clark over the British in 1779. In 1800, what is now Polk County was part of the Indiana Territory. In 1809 it was part of the Illinois Territory, and in 1818 part of the Michigan Territory and Crawford County. In 1836 it became part of the Wisconsin Territory.

The first settlement was made at St. Croix Falls in 1837 by Franklin Steele, Georgw W. Fitch, Emerson maginnis and others. In 1840 the first post office, named Falls of the St. Croix, was established. In that year Polk County was part of St. Croix County.

The next settlement was started in 1844 at Osceola Mills, now Osceola. William Kent settled here and established a sawmill. Logging and lumbering became the main industry, as virgin pine logs were floated down the St. Croix River. In those early years the settlers came up the St. Croix to Osceola Mills and St. Croix Falls by steamboat.

Wisconsin became a state in 1848, and Polk County, named after James K. Polk, 11th president of the United States, was formed in 1853. The county seat was at Osceola Mills, which had its first post office in 1854. Several frame buildings served as the courthouse until 1862, when a sandstone building on Osceola's main street, was used.

In 1899 a new courthouse was built in Balsam Lake, as the voters chose the centrally-located site as the county seat. That courthouse building now houses the Polk County Historical Society.