Black Hawk County is a county in the northeastern part of the U.S. state of Iowa. As of the 2020 census, the population was 131,144, making it Iowa's fifth-most populous county. The county seat is Waterloo.

Black Hawk County is part of the Waterloo – Cedar Falls metropolitan area.

Black Hawk County was formed on February 17, 1853, from sections of Buchanan County. It was named after Black Hawk, a Sauk leader during the 1832 Black Hawk War.

According to the U.S. Census Bureau, the county has an area of 573 square miles (1,480 km), of which 566 square miles (1,470 km) is land and 6.9 square miles (18 km) (1.2%) is water.

The Cedar River roughly divides the county in half from the northwest to the southeast corner. The land is mostly level since much of it is on the river's flood plain.

• Metropolitan Transit Authority of Black Hawk County
• List of intercity bus stops in Iowa

• Bremer County (north)
• Buchanan County (east)
• Benton County (southeast)
• Tama County (southwest)
• Grundy County (west)
• Butler County (northwest)
• Fayette County (northeast)

Historical population

Census	Pop.	Note	%±
1850	135		—
1860	8,244		6,006.7%
1870	21,706		163.3%
1880	23,913		10.2%
1890	24,219		1.3%
1900	32,399		33.8%
1910	44,865		38.5%
1920	56,570		26.1%
1930	69,146		22.2%
1940	79,946		15.6%
1950	100,448		25.6%
1960	122,482		21.9%
1970	132,916		8.5%
1980	137,961		3.8%
1990	123,798		−10.3%
2000	128,012		3.4%
2010	131,090		2.4%
2020	131,144		0.0%
2023 (est.)	130,471		−0.5%
U.S. Decennial Census 1790-1960 1900-1990 1990-2000 2010-2019

The 2020 census recorded a population of 131,144 in the county, with a population density of 229.5011/sq mi (88.6109/km). 94.55% of the population reported being of one race. 73.49% were White, 10.43% were Black, 4.92% were Hispanic, 0.32% were Native American, 2.61% were Asian, 0.65% were Native Hawaiian or Pacific Islander and 7.57% were some other race or more than one race. There were 58,559 housing units of which 54,223 were occupied.

The 2010 census recorded a population of 131,090 in the county, with a population density of 231.20/sq mi (89.27/km). There were 55,887 housing units, of which 52,470 were occupied.

At the 2000 census there were 128,012 people, 49,683 households, and 31,946 families in the county. The population density was 226 inhabitants per square mile (87/km). There were 51,759 housing units at an average density of 91 per square mile (35/km). The racial makeup of the county was 88.42% White, 7.95% Black or African American, 0.18% Native American, 0.98% Asian, 0.04% Pacific Islander, 0.93% from other races, and 1.49% from two or more races. 1.84%. were Hispanic or Latino of any race.

Of the 49,683 households 29.50% had children under the age of 18 living with them, 50.20% were married couples living together, 10.80% had a female householder with no husband present, and 35.70% were non-families. 27.10% of households were one person and 10.90% were one person aged 65 or older. The average household size was 2.45 and the average family size was 2.97.

Age spread: 23.10% under the age of 18, 15.70% from 18 to 24, 25.20% from 25 to 44, 22.00% from 45 to 64, and 14.00% 65 or older. The median age was 34 years. For every 100 females, there were 92.30 males. For every 100 females age 18 and over, there were 88.80 males.

The median household income was $37,266 and the median family income was $47,398. Males had a median income of $33,138 versus $23,394 for females. The per capita income for the county was $18,885. About 7.90% of families and 13.10% of the population were below the poverty line, including 14.40% of those under age 18 and 8.90% of those age 65 or over.

• Washburn

• Blessing
• Dewar
• Eagle Center
• Finchford
• Glasgow
• Voorhies

Black Hawk County is divided into seventeen townships:

The population ranking of the following table is based on the 2020 census of Black Hawk County.

† county seat

Rank	City/Town/etc.	Municipal type	Population (2020 Census)
1	† Waterloo	City	67,314
2	Cedar Falls	City	40,713
3	Evansdale	City	4,561
4	Hudson	City	2,546
5	Jesup (mostly in Buchanan County)	City	193 (2508 total)
6	La Porte City	City	2,284
7	Elk Run Heights	City	1,069
8	Janesville (mostly in Bremer County)	City	115 (1034 total)
9	Washburn	CDP	870
10	Dunkerton	City	842
11	Gilbertville	City	794
12	Raymond	City	759

Black Hawk County has been a Democratic stronghold in Iowa since the late 1980s. In presidential politics, it is one of the most Democratic counties in Iowa. As the state swung hard to the right in the 2010s and 2020s, Black Hawk County—as a major population center, in accordance with most other population centers nationwide—has remained staunchly Democratic. In 2016, however, Donald Trump became the first Republican since 1984 to hold the Democratic candidate's margin to under 10 percent, something he repeated in 2020 albeit with reduced margins.

United States presidential election results for Black Hawk County, Iowa

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	30,572	48.60%	31,299	49.76%	1,035	1.65%
2020	29,640	44.51%	35,647	53.53%	1,306	1.96%
2016	27,476	42.66%	32,233	50.05%	4,696	7.29%
2012	26,235	39.07%	39,821	59.31%	1,085	1.62%
2008	24,662	38.07%	39,184	60.48%	941	1.45%
2004	28,046	43.89%	35,392	55.38%	469	0.73%
2000	23,468	42.60%	30,112	54.66%	1,505	2.73%
1996	19,322	36.38%	29,651	55.83%	4,136	7.79%
1992	21,398	34.77%	29,584	48.06%	10,568	17.17%
1988	24,112	42.93%	31,657	56.36%	402	0.72%
1984	32,262	50.23%	31,467	48.99%	504	0.78%
1980	29,627	46.49%	27,443	43.07%	6,652	10.44%
1976	30,994	50.22%	29,508	47.81%	1,213	1.97%
1972	30,929	57.51%	21,721	40.39%	1,132	2.10%
1968	25,594	51.65%	21,097	42.57%	2,863	5.78%
1964	19,744	39.08%	30,716	60.80%	56	0.11%
1960	28,435	54.11%	24,078	45.82%	38	0.07%
1956	28,250	57.99%	20,403	41.88%	66	0.14%
1952	28,671	62.01%	17,360	37.55%	203	0.44%
1948	16,041	44.28%	19,603	54.11%	586	1.62%
1944	15,687	48.37%	16,593	51.16%	154	0.47%
1940	17,132	49.61%	17,305	50.11%	95	0.28%
1936	13,666	43.14%	16,793	53.01%	1,222	3.86%
1932	14,746	49.54%	14,660	49.25%	359	1.21%
1928	19,409	69.35%	8,467	30.25%	113	0.40%
1924	15,813	65.29%	2,981	12.31%	5,427	22.41%
1920	16,920	76.56%	4,000	18.10%	1,181	5.34%
1916	6,742	59.34%	4,270	37.58%	349	3.07%
1912	1,601	15.03%	3,702	34.76%	5,346	50.20%
1908	5,437	59.67%	3,127	34.32%	548	6.01%
1904	5,236	66.90%	1,861	23.78%	730	9.33%
1900	5,010	64.39%	2,512	32.28%	259	3.33%
1896	4,643	66.05%	2,167	30.83%	220	3.13%
1892	3,483	57.08%	2,544	41.69%	75	1.23%
1888	3,106	58.50%	2,127	40.06%	76	1.43%
1884	3,153	60.21%	2,084	39.79%	0	0.00%
1880	3,014	64.57%	1,558	33.38%	96	2.06%

• National Register of Historic Places listings in Black Hawk County, Iowa
• Impact of the 2019–20 coronavirus pandemic on the meat industry in the United States

• Black Hawk County government's website

42°28′08″N 92°18′19″W / 42.46889°N 92.30528°W / 42.46889; -92.30528