Blue Earth County is a county in the State of Minnesota. As of the 2020 census, the population was 69,112. Its county seat is Mankato. The county is named for the Blue Earth River and for the deposits of blue-green clay once evident along the banks of the Blue Earth River. Blue Earth County is part of the Mankato-North Mankato metropolitan area.

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Dakota people lived and hunted in the area of Blue Earth County, particularly the Sisseton. French explorer Pierre-Charles Le Sueur was an early European explorer in this area, arriving where the Minnesota and Blue Earth rivers meet. He made an unsuccessful attempt to mine copper from the blue-green clay the Dakota used as paint. The area remained under French control until 1803 when it passed to the United States in the Louisiana Purchase.

When Minnesota became a territory in 1849, the territorial government became interested in settling the river valley. In 1850 the first steamboat trip, starting in St. Paul, traveled on the Minnesota River and came to the Blue Earth River. The first Euro-American settlers, P. K. Johnson and Henry Jackson, debarked and settled in present-day Mankato. The ratification of the Mendota and Traverse des Sioux treaties in 1851 effectively forced the eastern Dakota to move to nearby reservations.

The county of Blue Earth was created after a division of the Minnesota Territory on March 5, 1853, from portions of Dakota County and free territory. It was named for the Blue Earth River. The first government officials were appointed by Alexander Ramsey, the territorial governor. That October the first election was held, with 22 ballots being taken.

On February 27, 1855, the Winnebago (Ho-Chunk) ceded 897,900 acres (363,400 ha) of their reservation near Long Prairie in exchange for 200,000 acres (81,000 ha) on the Blue Earth River. On May 24, 1855, they relocated and became so successful at farming that neighboring American settlers coveted their land.

Blue Earth County is near the Lower Sioux reservation, which was created in 1858. Starvation on the reservation and the lack of timely arrival of government annuities led to the Dakota War of 1862, followed by removal of all Native Americans from the county. In 1868 the railroad's arrival promoted the county's growth and development by bringing immigrants and goods to the area.

The Minnesota River flows southeasterly along the western part of the county's northern boundary line. It is joined by the Blue Earth River, which flows northerly through the western central part of the county. The Watonwan River flows northwesterly through the northeastern part of the county, discharging into the Blue Earth. The Little Cobb River flows northwesterly through the southeastern part of the county, meeting with the Cobb River which flows northerly through the lower part of the county into the Blue Earth River. The Le Sueur River also flows west-northwesterly through the SE part of the county, discharging into the Blue Earth River.

The county terrain consists of low rolling hills, with the area (except around built-up zones, and in areas carved by runoff) devoted to agriculture. It slopes generally to the north. Its southwest corner is 1,086 ft (331 m) above sea level.

The county has an area of 766 square miles (1,980 km), of which 748 square miles (1,940 km) is land and 18 square miles (47 km) (2.3%) is water. The Blue Earth River and Le Sueur River flow through a part of the county. The land surface is relatively flat with over 30 lakes in the county. There are many "closed forest savannas" that some call the big woods in the county's northeast. The rivers that flow out of the northeast are surrounded by these big woods. Most of the county is grassland prairie but scattered parts are wet prairie. Some spots that surround the rivers are oak openings and barren brushland.

Mankato, Minnesota
Climate chart (explanation)
J F M A M J J A S O N D     0.9     24 5     0.8     30 10     2     42 22     3.1     58 35     3.5     70 47     5.1     79 57     4.3     83 62     4.2     81 59     3.2     73 49     2.3     60 37     1.9     43 24     1.1     28 11 █ Average max. and min. temperatures in °F █ Precipitation totals in inches Source: The Weather Channel
Metric conversion J F M A M J J A S O N D     24     −4 −15     20     −1 −12     50     6 −6     78     14 2     88     21 8     129     26 14     110     28 17     106     27 15     82     23 9     59     16 3     49     6 −4     28     −2 −12 █ Average max. and min. temperatures in °C █ Precipitation totals in mm

In recent years, average temperatures in the county seat of Mankato have ranged from a low of 5 °F (−15 °C) in January to a high of 83 °F (28 °C) in July, although a record low of −35 °F (−37 °C) was recorded in February 1996 and a record high of 107 °F (42 °C) was recorded in August 1988. Average monthly precipitation ranged from 0.78 inches (20 mm) in February to 5.09 inches (129 mm) in June.

Historical population

Census	Pop.	Note	%±
1860	4,803		—
1870	17,302		260.2%
1880	22,889		32.3%
1890	29,210		27.6%
1900	32,263		10.5%
1910	29,337		−9.1%
1920	31,477		7.3%
1930	33,847		7.5%
1940	36,203		7.0%
1950	38,327		5.9%
1960	44,385		15.8%
1970	52,322		17.9%
1980	52,314		0.0%
1990	54,044		3.3%
2000	55,941		3.5%
2010	64,013		14.4%
2020	69,112		8.0%
2023 (est.)	70,006		1.3%
U.S. Decennial Census 1790-1960 1900-1990 1990-2000 2010-2020

Blue Earth County Racial Composition

Race	Num.	Perc.
White (NH)	57,222	82.8%
Black or African American (NH)	3,873	5.6%
Native American (NH)	208	0.3%
Asian (NH)	1,834	2.7%
Pacific Islander (NH)	24	0.03%
Other/Mixed (NH)	2730	4%
Hispanic or Latino	3,221	4.7%

As of the census of 2000, the county had 55,941 people, 21,062 households, and 12,616 families. The population density was 74.8 per square mile (28.9/km). There were 21,971 housing units at an average density of 29.4 per square mile (11.4/km). The county's racial makeup was 94.96% White, 1.19% Black or African American, 0.28% Native American, 1.79% Asian, 0.06% Pacific Islander, 0.69% from other races, and 1.03% from two or more races. 1.77% of the population were Hispanic or Latino of any race. 47.6% were of German, 13.6% Norwegian and 6.5% Irish ancestry.

There were 21,062 households, of which 29.10% had children under the age of 18 living with them, 48.60% were married couples living together, 7.80% had a female householder with no husband present, and 40.10% were non-families. 27.10% of all households were made up of individuals, and 9.50% had someone living alone who was 65 years of age or older. The average household size was 2.46 and the average family size was 2.99.

21.40% of the county's population was under the age of 18, 22.10% were from age 18 to 24, 25.60% were from age 25 to 44, 18.80% were from age 45 to 64, and 12.10% were age 65 or older. The median age was 30 years. For every 100 females, there were 99.10 males. For every 100 females age 18 and over, there were 97.40 males.

The county's median household income was $38,940, and the median family income was $50,257. Males had a median income of $32,087 versus $22,527 for females. The county's per capita income was $18,712. About 6.10% of families and 12.90% of the population were below the poverty line, including 10.50% of those under age 18 and 9.40% of those age 65 or over.

• Garden City

• Cambria
• Marysburg
• Perth
• Smiths Mill

Since 1952, Blue Earth County has voted for the winning presidential candidate in 16 of the last 19 elections, the exceptions being 1960, 1988 and 2004. Blue Earth County is considered a college town due to the presence of Minnesota State University in Mankato.

United States presidential election results for Blue Earth County, Minnesota

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	18,001	49.40%	17,558	48.18%	883	2.42%
2020	16,731	46.41%	18,330	50.84%	990	2.75%
2016	15,667	46.64%	14,428	42.95%	3,498	10.41%
2012	14,916	43.52%	18,164	53.00%	1,194	3.48%
2008	14,782	42.15%	19,325	55.10%	963	2.75%
2004	15,737	47.52%	16,865	50.92%	517	1.56%
2000	12,942	47.23%	12,329	44.99%	2,131	7.78%
1996	9,082	35.95%	12,420	49.17%	3,759	14.88%
1992	8,813	31.65%	11,531	41.41%	7,503	26.94%
1988	11,959	48.71%	12,375	50.40%	218	0.89%
1984	14,298	54.27%	11,877	45.08%	172	0.65%
1980	11,966	45.78%	10,930	41.82%	3,242	12.40%
1976	11,998	46.71%	12,930	50.33%	760	2.96%
1972	12,702	53.68%	10,638	44.96%	322	1.36%
1968	9,571	48.99%	9,254	47.37%	712	3.64%
1964	8,009	42.61%	10,687	56.85%	101	0.54%
1960	11,328	58.35%	8,052	41.48%	33	0.17%
1956	11,398	67.50%	5,467	32.38%	21	0.12%
1952	11,867	70.34%	4,952	29.35%	51	0.30%
1948	7,520	50.29%	7,272	48.63%	162	1.08%
1944	9,429	64.67%	5,098	34.96%	54	0.37%
1940	9,642	61.87%	5,880	37.73%	62	0.40%
1936	5,550	37.58%	8,255	55.89%	964	6.53%
1932	5,550	40.54%	7,925	57.88%	216	1.58%
1928	8,120	60.71%	5,177	38.70%	79	0.59%
1924	6,773	55.09%	1,123	9.13%	4,399	35.78%
1920	8,894	79.05%	1,974	17.55%	383	3.40%
1916	2,864	53.96%	2,211	41.65%	233	4.39%
1912	1,344	25.40%	2,025	38.27%	1,922	36.33%
1908	3,297	56.20%	2,191	37.34%	379	6.46%
1904	3,573	67.42%	1,419	26.77%	308	5.81%
1900	3,647	58.68%	2,254	36.27%	314	5.05%
1896	4,055	57.50%	2,744	38.91%	253	3.59%
1892	2,680	46.00%	2,399	41.18%	747	12.82%
1888	3,307	51.04%	2,761	42.61%	411	6.34%
1884	2,480	51.66%	2,028	42.24%	293	6.10%
1880	2,680	52.64%	2,399	47.12%	12	0.24%
1876	2,140	51.21%	2,039	48.79%	0	0.00%
1872	1,906	54.10%	1,617	45.90%	0	0.00%
1868	1,749	63.07%	1,024	36.93%	0	0.00%
1864	962	63.00%	565	37.00%	0	0.00%
1860	2,680	52.52%	2,399	47.01%	24	0.47%

County Board of Commissioners

Position		Name	District	Next Election
	Commissioner	Patty O'Connor	District 1	2026
	Commissioner and Chairperson	Vance Stuehrenberg	District 2	2024
	Commissioner	Mark Piepho	District 3	2024
	Commissioner and Vice Chair	Kevin Paap	District 4	2026
	Commissioner	Kip Bruender	District 5	2026

State Legislature (2021-2023)

Position		Name	Affiliation	District
	Senate	Nick Frentz	Democrat	District 19
	Senate	Julie Rosen	Republican	District 23
	House of Representatives	Susan Akland	Republican	District 19A
	House of Representatives	Luke Frederick	Democrat	District 19B
	House of Representatives	Jeremy Munson	Republican	District 23B

U.S Congress (2021-2023)

Position		Name	Affiliation	District
	House of Representatives	Brad Finstad	Republican	1st
	Senate	Amy Klobuchar	Democrat	N/A
	Senate	Tina Smith	Democrat	N/A

• National Register of Historic Places listings in Blue Earth County, Minnesota

• Blue Earth County Government’s website

44°02′N 94°04′W / 44.03°N 94.06°W / 44.03; -94.06