Patches of woodland are all that remain of the brush and light forest that once covered the county. In ancient times, the woodlands contained a great deal of timber, but Native Americans burned them periodically to encourage the growth of berries. They did little cultivation and had been almost completely removed from the area by 1837. French fur traders were the first Europeans to enter this land, traveling by river across the county. At the mouth of the Trempealeau River at its confluence with the Mississippi River, they found a bluff surrounded by water and called it La Montagne qui trempe à l’eau. It is now known as Trempealeau Mountain. The name was later shortened to Trempealeau. Created in 1854 and organized in 1855, the county is named after the river. During the 19th and 20th century large numbers of Norwegian immigrants settled in the area in pursuit of cheap land, a better life and more opportunities. Much of the population is still of Norwegian descent and celebrate their ancestry by making foods native to Norway and participating in Norwegian Constitution Day events.
Geography
According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. It is part of the Driftless Zone.
As of the census of 2000, there were 27,010 people, 10,747 households, and 7,243 families residing in the county. The population density was. There were 11,482 housing units at an average density of 16 per square mile. The racial makeup of the county was 98.81% White, 0.13% Black or African American, 0.17% Native American, 0.13% Asian, 0.01% Pacific Islander, 0.29% from other races, and 0.47% from two or more races. 0.89% of the population were Hispanic or Latino of any race. 43.5% were of Norwegian, 24.6% German and 17.0% Polish ancestry. 94.9% spoke English, 1.6% Norwegian and 1.6% Spanish as their first language. There were 10,747 households out of which 31.80% had children under the age of 18 living with them, 55.20% were married couplesliving together, 7.40% had a female householder with no husband present, and 32.60% were non-families. 27.60% of all households were made up of individuals and 13.50% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 3.00. In the county, the population was spread out with 25.30% under the age of 18, 6.90% from 18 to 24, 28.20% from 25 to 44, 23.10% from 45 to 64, and 16.40% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 100.30 males. For every 100 females age 18 and over, there were 98.80 males. In 2017, there were 450 births, giving a general fertility rate of 93.1 births per 1000 women aged 15–44, the third highest rate out of all 72 Wisconsin counties.
