In 1849, the newly organized Minnesota Territory legislature authorized nine counties across the territory. One of those, Dakota, was partially subdivided in 1853 to create Blue Earth, Le Sueur, and Rice counties. In 1855, parts of those counties were partitioned to create Steele. On February 27, 1857, the territorial legislature authorized partitioning western Steele County to create Waseca County, with its seat at Wilton, a settlement which began in 1854. The county name was taken from the area's first farming settlement, started in 1855, near the present location of the city of Waseca. That settlement name came from the Dakota word meaning "rich," a reference to the fertile soil in the area.
The Winona and Saint Peter Railroad line past the town of Waseca was completed in the latter half of the 1860s, causing the town to bloom. By 1870 the vote was taken to relocate the county seat to that settlement.[5]
Waseca County's boundaries have not changed since its creation.
The Le Sueur River flows westward through the county toward its confluence with the Blue Earth River in Blue Earth County. It is augmented by the Little Le Sueur, which drains the southeast part of the county. Bull Run Creek flows westward from Silver Lake through the lower central part of the county into Blue Earth County; the Little Cobb River rises in southern Waseca County and flows westward into Blue Earth County to its confluence with the Cobb River.
The county terrain consists of low rolling hills, carved by drainages and dotted with lakes. The area is devoted to agriculture wherever possible.[7] The terrain slopes to the north and west, with its highest point near its southeast corner, at 1,240 ft (380 m) ASL.[8] The county has an area of 433 square miles (1,120 km2), of which 423 square miles (1,100 km2) is land and 9.6 square miles (25 km2) (2.2%) is water.[9]
Waseca is one of seven southern Minnesota counties that have no forest ecosystems, only prairie and savanna soils.
As of the census of 2000, there were 19,526 people, 7,059 households, and 4,990 families in the county. The population density was 46.2 per square mile (17.8/km2). There were 7,427 housing units at an average density of 17.6 per square mile (6.8/km2). The racial makeup of the county was 94.65% White, 2.26% Black or African American, 0.59% Native American, 0.46% Asian, 0.03% Pacific Islander, 1.29% from other races, and 0.71% from two or more races. 2.90% of the population were Hispanic or Latino of any race. 47.6% were of German, 15.5% Norwegian, 7.4% Irish and 5.5% American ancestry.
There were 7,059 households, of which 34.7% had children under the age of 18 living with them, 59.0% were married couples living together, 7.8% had a female householder with no husband present, and 29.3% were non-families. 25.1% of all households were made up of individuals, and 10.70% had someone living alone who was 65 or older. The average household size was 2.56 and the average family size was 3.07.
The county population contained 25.8% under 18, 8.7% from 18 to 24, 30.0% from 25 to 44, 21.3% from 45 to 64, and 14.2% who were 65 or older. The median age was 36. For every 100 females there were 109.3 males. For every 100 females 18 and over, there were 111.3 males.
The median income for a household in the county was $42,440, and the median income for a family was $50,081. Males had a median income of $34,380 versus $22,630 for females. The per capita income was $18,631. About 4.5% of families and 6.5% of the population were below the poverty line, including 8.8% of those under 18 and 5.8% of those 65 or over.
Waseca County has traditionally voted Republican. In only three presidential elections since 1936 has the county selected the Democratic nominee (as of 2024).
