Knox County is a county in the U.S. state of Illinois. According to the 2020 census, it had a population of 49,967. Its county seat is Galesburg.

Knox County comprises the Galesburg, IL Micropolitan Statistical Area.

Knox County was named in honor of Henry Knox, the first US Secretary of War.

The first "Knox County" in what today is Illinois was unrelated to the modern incarnation. In 1790, the land of the Indiana Territory that was to become Illinois was divided into two counties: St. Clair and Knox. The latter included land in what was to become Indiana. When Knox County, Indiana, was formed from this portion of the county in 1809, the Illinois portions were subdivided into counties that were given other names.

The modern Knox County, Illinois, was organized in 1825, from Fulton County, itself a portion of the original St. Clair County.

Like its neighbor to the south, Fulton County, for its Spoon River Drive, Knox County is also known for a similar scenic drive fall festival the first two weekends in October, the Knox County Drive.

• 
  Knox County between its creation in 1825 and 1831
• 
  Knox County between 1831 and 1839
• 
  Knox County in 1839, when it was reduced slightly to its current size

According to the U.S. Census Bureau, the county has a total area of 720 square miles (1,900 km), of which 716 square miles (1,850 km) is land and 3.4 square miles (8.8 km) (0.5%) is water.

Galesburg, Illinois
Climate chart (explanation)
J F M A M J J A S O N D     1.4     29 13     1.6     35 19     2.8     48 29     3.8     61 40     4     73 51     4.2     81 61     4.4     85 65     4.1     82 63     3.5     75 55     2.5     63 43     2.7     47 31     2.3     33 19 █ 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     36     −2 −11     39     2 −7     72     9 −2     97     16 4     101     23 11     106     27 16     111     29 18     103     28 17     89     24 13     64     17 6     69     8 −1     58     1 −7 █ Average max. and min. temperatures in °C █ Precipitation totals in mm

In recent years, average temperatures in the county seat of Galesburg have ranged from a low of 13 °F (−11 °C) in January to a high of 85 °F (29 °C) in July, although a record low of −25 °F (−32 °C) was recorded in January 1982 and a record high of 102 °F (39 °C) was recorded in July 1983. Average monthly precipitation ranged from 1.41 inches (36 mm) in January to 4.37 inches (111 mm) in July.

• Galesburg station
• Burlington Trailways
• Galesburg Transit
• List of intercity bus stops in Illinois

• Mercer County - northwest
• Henry County - north
• Stark County - east
• Peoria County - southeast
• Fulton County - south
• Warren County - west

Historical population

Census	Pop.	Note	%±
1830	274		—
1840	7,060		2,476.6%
1850	13,279		88.1%
1860	28,663		115.9%
1870	39,522		37.9%
1880	38,344		−3.0%
1890	38,752		1.1%
1900	43,612		12.5%
1910	46,159		5.8%
1920	46,727		1.2%
1930	51,336		9.9%
1940	52,250		1.8%
1950	54,366		4.0%
1960	61,280		12.7%
1970	61,280		0.0%
1980	61,607		0.5%
1990	56,393		−8.5%
2000	55,836		−1.0%
2010	52,919		−5.2%
2020	49,967		−5.6%
2023 (est.)	48,411		−3.1%
U.S. Decennial Census 1790-1960 1900-1990 1990-2000 2010-2013

As of the 2010 United States Census, there were 52,919 people, 21,535 households, and 13,324 families residing in the county. The population density was 73.9 inhabitants per square mile (28.5/km). There were 24,077 housing units at an average density of 33.6 per square mile (13.0/km). The racial makeup of the county was 87.5% white, 7.2% black or African American, 0.6% Asian, 0.2% American Indian, 1.9% from other races, and 2.5% from two or more races. Those of Hispanic or Latino origin made up 4.8% of the population. In terms of ancestry, 23.1% were German, 14.9% were Irish, 11.7% were English, 11.6% were Swedish, and 8.0% were American.

Of the 21,535 households, 27.2% had children under the age of 18 living with them, 45.7% were married couples living together, 11.9% had a female householder with no husband present, 38.1% were non-families, and 32.3% of all households were made up of individuals. The average household size was 2.27 and the average family size was 2.84. The median age was 42.0 years.

The median income for a household in the county was $39,545 and the median income for a family was $51,740. Males had a median income of $42,067 versus $25,380 for females. The per capita income for the county was $20,908. About 10.9% of families and 15.5% of the population were below the poverty line, including 24.7% of those under age 18 and 7.3% of those age 65 or over.

• Abingdon
• Galesburg
• Knoxville
• Oneida

• Gilson
• Oak Run

Knox County is divided into twenty-one townships:

Knox County's political history is typical of Yankee-settled Northern Illinois. It leaned Whig during its early elections – although giving a plurality to Franklin Pierce in 1852 – and become powerfully Republican following that party's formation. Although Knox did support Progressive Theodore Roosevelt against conservative incumbent President William Howard Taft in 1912, it was Franklin D. Roosevelt’s 1932 landslide before Knox County again gave the Democratic Party so much as a plurality, and it did not give a Democratic absolute majority until Lyndon B. Johnson gained such against the anti-Yankee, Southern-leaning Barry Goldwater in 1964.

Since then, Knox County gradually trended Democratic for the following four decades, so that Michael Dukakis in his losing 1988 campaign was able to carry the county by the same margin as Johnson had done in 1964. During the 1990s and 2000s, Knox was a solidly Democratic county, voting Democratic by at least nine percentage points in every election from 1992 to 2012. The 2016 election, in the shadow of high unemployment in the “Rust Belt” saw a swing of over twenty percentage points to Donald Trump, who became the first Republican victor in the county since Ronald Reagan in 1984.

United States presidential election results for Knox County, Illinois

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2020	12,009	51.75%	10,703	46.12%	496	2.14%
2016	10,737	47.71%	10,083	44.81%	1,683	7.48%
2012	9,408	40.28%	13,451	57.59%	497	2.13%
2008	9,419	39.09%	14,191	58.89%	488	2.03%
2004	11,111	44.97%	13,403	54.25%	194	0.79%
2000	9,912	42.77%	12,572	54.25%	690	2.98%
1996	7,822	34.69%	12,487	55.38%	2,239	9.93%
1992	8,331	32.93%	12,524	49.51%	4,441	17.56%
1988	10,842	45.75%	12,752	53.81%	106	0.45%
1984	14,974	55.21%	12,027	44.34%	121	0.45%
1980	14,907	56.90%	8,749	33.40%	2,542	9.70%
1976	14,123	54.39%	11,525	44.38%	319	1.23%
1972	17,315	64.69%	9,333	34.87%	118	0.44%
1968	14,216	53.86%	9,707	36.77%	2,473	9.37%
1964	12,850	46.14%	15,000	53.86%	0	0.00%
1960	17,938	60.09%	11,889	39.83%	23	0.08%
1956	18,656	66.04%	9,558	33.83%	37	0.13%
1952	18,569	64.16%	10,354	35.78%	17	0.06%
1948	15,016	60.18%	9,772	39.16%	164	0.66%
1944	15,964	61.02%	10,070	38.49%	126	0.48%
1940	17,459	57.77%	12,597	41.68%	168	0.56%
1936	14,712	50.52%	13,697	47.03%	715	2.46%
1932	12,244	49.14%	12,282	49.29%	392	1.57%
1928	16,151	72.33%	5,993	26.84%	186	0.83%
1924	12,968	65.89%	2,617	13.30%	4,095	20.81%
1920	12,559	73.85%	2,852	16.77%	1,594	9.37%
1916	10,918	58.82%	6,785	36.55%	860	4.63%
1912	1,750	16.72%	2,758	26.35%	5,959	56.93%
1908	7,084	63.83%	3,277	29.53%	737	6.64%
1904	7,566	73.84%	1,849	18.04%	832	8.12%
1900	7,810	67.62%	3,299	28.57%	440	3.81%
1896	7,681	67.39%	3,480	30.53%	236	2.07%
1892	5,800	60.49%	3,073	32.05%	715	7.46%

• National Register of Historic Places listings in Knox County, Illinois

• Charles C. Chapman and Co., History of Knox County, Illinois: Together with Sketches of the Cities, Villages and Townships; Record of its Volunteers in the Late War; Educational, Religious, Civil and Political History; Portraits of Prominent Persons and Biographical Sketches of the Subscribers; History of Illinois, Abstracts of the State Laws, Etc., Etc., Etc. Chicago: Blakely, Brown and Marsh, Printers, 1878.
• Fred R. Jelliff, Annals of Knox County: Commemorating Centennial of Admission of Illinois as State of the Union in 1818. Galesburg, IL: Republican Register Printing, 1918.
• Portrait and Biographical Album of Knox County, Illinois, Containing Full Page Portraits and Biographical Sketches of Prominent and Representative Citizens of the County, Together with Portraits and Biographies of All the Governors of Illinois, and of the Presidents of the United States: Also Containing a History of the County from Its Earliest Settlement Up to the Present Time. Chicago: Biographical Publishing Company, 1886.

• "Foxie's Knox Co., IL AHGP"

40°56′N 90°13′W / 40.93°N 90.21°W / 40.93; -90.21