Harrison County is a county located in the U.S. state of Ohio. As of the 2020 census, the population was 14,483, making it the fifth-least populous county in Ohio. Its county seat and largest village is Cadiz. The county is named for General William Henry Harrison, who was later President of the United States.

Harrison County was formed from parts of Jefferson and Tuscarawas Counties in 1813. The county was named after General William Henry Harrison, the hero of the battle of Tippecanoe in the War of 1812 (and later to become the ninth U.S. president).

Oil was discovered near Jewett, Ohio in 1895, and then in the Scio, Ohio area in 1898. However, by 1901, the Scio oil boom had essentially ceased.

According to the U.S. Census Bureau, the county has a total area of 411 square miles (1,060 km), of which 402 square miles (1,040 km) is land and 8.4 square miles (22 km) (2.1%) is water.

On May 16, 2013, the Chicago Tribune Business section reported that the Utica Shale underlying Harrison County shows promise as a tight oil production zone. To produce tight oil in large quantities would require horizontal drilling and fracturing of the shale formation as is being done in North Dakota and Texas.

• Carroll County (north)
• Jefferson County (east)
• Belmont County (south)
• Guernsey County (southwest)
• Tuscarawas County (west)

The Conotton Creek Trail is a rails-to-trails path that runs along Conotton Creek from Bowerston to Jewett in northern Harrison County, Ohio. The paved multi-use trail is 11.4 miles (18.3 km) long.

Historical population

Census	Pop.	Note	%±
1820	14,345		—
1830	20,916		45.8%
1840	20,099		−3.9%
1850	20,157		0.3%
1860	19,110		−5.2%
1870	18,682		−2.2%
1880	20,456		9.5%
1890	20,830		1.8%
1900	20,486		−1.7%
1910	19,076		−6.9%
1920	19,625		2.9%
1930	18,844		−4.0%
1940	20,313		7.8%
1950	19,054		−6.2%
1960	17,995		−5.6%
1970	17,013		−5.5%
1980	18,152		6.7%
1990	16,085		−11.4%
2000	15,856		−1.4%
2010	15,864		0.1%
2020	14,483		−8.7%
U.S. Decennial Census 1790-1960 1900-1990 1990-2000 2020

As of the census of 2000, there were 15,856 people, 6,398 households, and 4,516 families living in the county. The population density was 39 people per square mile (15 people/km). There were 7,680 housing units at an average density of 19 units per square mile (7.3/km). The racial makeup of the county was 96.49% White, 2.19% Black or African American, 0.08% Native American, 0.11% Asian, 0.01% Pacific Islander, 0.09% from other races, and 1.03% from two or more races. 0.37% of the population were Hispanic or Latino of any race.

There were 6,398 households, out of which 29.1% had children under the age of 18 living with them, 58.5% were married couples living together, 8.8% had a female householder with no husband present, and 29.4% were non-families. 25.6% of all households were made up of individuals, and 13% had someone living alone who was 65 years of age or older. The average household size was 2.44 and the average family size was 2.92.

In the county, the population was spread out, with 23% under the age of 18, 6.9% from 18 to 24, 26.6% from 25 to 44, 25.8% from 45 to 64, and 17.7% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 94.1 males. For every 100 females age 18 and over, there were 89.9 males.

The median income for a household in the county was $30,318, and the median income for a family was $36,646. Males had a median income of $30,485 versus $18,813 for females. The per capita income for the county was $16,479. 13.3% of the population and 11% of families were below the poverty line. 17.5% of those under the age of 18 and 8.4% of those 65 and older were living below the poverty line.

As of the 2010 United States Census, there were 15,864 people, 6,526 households, and 4,452 families living in the county. The population density was 39.4 inhabitants per square mile (15.2/km). There were 8,170 housing units at an average density of 20.3 units per square mile (7.8 units/km). The racial makeup of the county was 95.9% white, 2.1% black or African American, 0.1% Asian, 0.1% American Indian, 0.1% from other races, and 1.6% from two or more races. Those of Hispanic or Latino origin made up 0.5% of the population. In terms of ancestry, 20.9% were German, 15.5% were Irish, 9.0% were English, 8.9% were American, and 5.7% were Polish.

Of the 6,526 households, 28.1% had children under the age of 18 living with them, 53.4% were married couples living together, 9.5% had a female householder with no husband present, 31.8% were non-families, and 27.1% of all households were made up of individuals. The average household size was 2.40 and the average family size was 2.88. The median age was 44.4 years.

The median income for a household in the county was $35,363 and the median income for a family was $44,325. Males had a median income of $38,489 versus $24,063 for females. The per capita income for the county was $19,318. About 14.1% of families and 18.4% of the population were below the poverty line, including 26.3% of those under age 18 and 12.6% of those age 65 or over.

Harrison County was considered a swing county in presidential elections prior to 2016. The last Democrat to win the county was Bill Clinton in 1996, although Al Gore came within 66 votes in 2000 and Barack Obama came within 189 votes in 2008.

United States presidential election results for Harrison County, Ohio

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	5,484	77.02%	1,559	21.90%	77	1.08%
2020	5,792	75.58%	1,768	23.07%	103	1.34%
2016	5,098	71.75%	1,688	23.76%	319	4.49%
2012	4,019	56.19%	2,950	41.24%	184	2.57%
2008	3,872	49.53%	3,683	47.12%	262	3.35%
2004	4,274	52.71%	3,780	46.61%	55	0.68%
2000	3,417	47.72%	3,351	46.80%	393	5.49%
1996	2,310	31.21%	3,721	50.27%	1,371	18.52%
1992	2,289	29.24%	3,830	48.93%	1,708	21.82%
1988	3,298	45.48%	3,881	53.52%	73	1.01%
1984	4,276	55.45%	3,370	43.70%	66	0.86%
1980	3,639	52.62%	2,848	41.18%	429	6.20%
1976	3,509	45.68%	4,070	52.99%	102	1.33%
1972	4,554	64.96%	2,388	34.07%	68	0.97%
1968	3,532	45.87%	3,594	46.68%	574	7.45%
1964	2,928	36.21%	5,159	63.79%	0	0.00%
1960	5,191	58.77%	3,641	41.23%	0	0.00%
1956	5,444	65.79%	2,831	34.21%	0	0.00%
1952	5,306	59.48%	3,614	40.52%	0	0.00%
1948	4,215	54.74%	3,422	44.44%	63	0.82%
1944	5,194	60.57%	3,381	39.43%	0	0.00%
1940	5,729	55.69%	4,559	44.31%	0	0.00%
1936	4,779	47.58%	5,231	52.08%	35	0.35%
1932	4,759	56.39%	3,512	41.62%	168	1.99%
1928	6,095	79.40%	1,516	19.75%	65	0.85%
1924	4,904	65.97%	1,999	26.89%	531	7.14%
1920	5,053	66.63%	2,473	32.61%	58	0.76%
1916	2,517	55.76%	1,911	42.33%	86	1.91%
1912	1,950	42.43%	1,714	37.29%	932	20.28%
1908	3,069	59.36%	1,961	37.93%	140	2.71%
1904	3,115	63.40%	1,578	32.12%	220	4.48%
1900	3,274	57.94%	2,261	40.01%	116	2.05%
1896	3,151	57.36%	2,245	40.87%	97	1.77%
1892	2,541	51.60%	2,032	41.27%	351	7.13%
1888	2,763	54.93%	1,927	38.31%	340	6.76%
1884	2,765	55.39%	2,077	41.61%	150	3.00%
1880	2,767	56.53%	2,082	42.53%	46	0.94%
1876	2,564	55.55%	2,020	43.76%	32	0.69%
1872	2,303	57.36%	1,695	42.22%	17	0.42%
1868	2,267	58.32%	1,620	41.68%	0	0.00%
1864	2,236	58.81%	1,566	41.19%	0	0.00%
1860	2,175	60.00%	759	20.94%	691	19.06%
1856	2,060	56.55%	1,473	40.43%	110	3.02%

• Tippecanoe

• John Bingham - Representative to Congress and author of significant portions of the Fourteenth Amendment to the Constitution
• Benjamin Cowen - Assistant Secretary of the Interior, who was principal political facilitator in establishing Yellowstone National Park and the idea that the use of national parks is for all Americans
• George Custer - served in the American Civil War and was killed in the Battle of Little Big Horn
• Thomas Custer - Medal of Honor recipient, and brother to George Custer
• Clark Gable - actor
• William Henry Holmes - anthropologist, archaeologist, geologist, and museum director
• Edwin Stanton - Secretary of War in the Abraham Lincoln administration

• National Register of Historic Places listings in Harrison County, Ohio
• Petroleum industry in Ohio

• Harrison County website
• Harrison County Sheriff's Office

40°17′N 81°05′W / 40.29°N 81.09°W / 40.29; -81.09