Dearborn County is one of 92 counties of the U.S. state of Indiana. Located on the Ohio border near the southeast corner of the state, Dearborn County was formed in 1803 from a portion of Hamilton County, Ohio. In 2020, the population was 50,679. The county seat and largest city is Lawrenceburg. Dearborn County is part of the Cincinnati, OH-KY-IN Metropolitan Statistical Area.

In 1803, following Ohio's admission to the Union, a wedge, or pie shaped, remnant of the former Northwest Territory along Ohio's southwestern border was ceded to Indiana Territory and organized as Dearborn County. It was named after Henry Dearborn who was U.S. Secretary of War at that time. Lawrenceburg was then designated as the county seat.

All or part of seven other present day counties were carved from the original county with the present boundaries being established in 1845. The region, nicknamed the "Gore", slices through the present-day counties of Dearborn, Franklin, Ohio, Randolph, Switzerland, Union, Wayne and Fayette. Subdivision of Dearborn County began in 1811 with the formation of Franklin and Wayne Counties, followed by Switzerland in 1814.

Early growth in the region was centered on Lawrenceburg which became an important railroad junction connecting two of the regions major rail lines. A contention existed between the towns of Lawrenceburg and the mostly German-speaking immigrants that dominated Rising Sun over the favored status of Lawrenceburg as the county seat. The rivalry between the two towns was resolved in 1844 when the Indiana State legislature separated the portion of Dearborn County south of Laughery Creek and created the last and smallest Indiana county, county of Ohio on March 1, 1844, with Rising Sun designated as its county seat.

According to the 2010 census, the county has a total area of 307.42 square miles (796.2 km), of which 305.03 square miles (790.0 km) (or 99.22%) is land and 2.38 square miles (6.2 km) (or 0.77%) is water. Part of the southeastern county line is formed by the Ohio River.

• Aurora
• Lawrenceburg
• Greendale

• Dillsboro
• Moores Hill
• Saint Leon
• West Harrison

• Bright
• Hidden Valley

• Franklin County (north)
• Butler County, Ohio (northeast)
• Hamilton County, Ohio (east)
• Boone County, Kentucky (southeast)
• Ohio County (south)
• Ripley County (west)

In recent years, average temperatures in Lawrenceburg have ranged from a low of 21 °F (−6 °C) in January to a high of 86 °F (30 °C) in July, although a record low of −27 °F (−33 °C) was recorded in January 1994 and a record high of 107 °F (42 °C) was recorded in July 1988. Average monthly precipitation ranged from 2.94 inches (75 mm) in September to 5.53 inches (140 mm) in May.

Lawrenceburg, Indiana
Climate chart (explanation)
J F M A M J J A S O N D     3.5     38 21     3     44 24     4.4     54 31     4.4     64 39     5.5     74 49     4.6     82 58     4.6     86 63     4     85 62     2.9     79 55     3.2     67 43     3.8     55 35     3.7     43 26 █ 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     89     3 −6     77     7 −4     111     12 −1     112     18 4     140     23 9     117     28 14     116     30 17     100     29 17     75     26 13     80     19 6     97     13 2     93     6 −3 █ Average max. and min. temperatures in °C █ Precipitation totals in mm

Historical population

Census	Pop.	Note	%±
1810	7,310		—
1820	11,468		56.9%
1830	13,974		21.9%
1840	19,327		38.3%
1850	20,166		4.3%
1860	24,406		21.0%
1870	24,116		−1.2%
1880	26,671		10.6%
1890	23,364		−12.4%
1900	22,194		−5.0%
1910	21,396		−3.6%
1920	20,033		−6.4%
1930	21,056		5.1%
1940	23,053		9.5%
1950	25,141		9.1%
1960	28,674		14.1%
1970	29,430		2.6%
1980	34,291		16.5%
1990	38,835		13.3%
2000	46,109		18.7%
2010	50,047		8.5%
2020	50,679		1.3%
2023 (est.)	51,215		1.1%
U.S. Decennial Census 1790-1960 1900-1990 1990-2000 2010-2013

At the 2010 United States Census, there were 50,047 people, 18,743 households and 13,773 families residing in the county. The population density was 164.1 inhabitants per square mile (63.4/km). There were 20,171 housing units at an average density of 66.1 per square mile (25.5/km). The racial makeup of the county was 97.5% white, 0.6% black or African American, 0.4% Asian, 0.2% American Indian, 0.1% Pacific islander, 0.3% from other races, and 1.0% from two or more races. Those of Hispanic or Latino origin made up 1.0% of the population. In terms of ancestry, 46.5% were German, 19.2% were Irish, 11.4% were English, and 7.8% were American.

Of the 18,743 households, 35.1% had children under the age of 18 living with them, 58.5% were married couples living together, 10.0% had a female householder with no husband present, 26.5% were non-families, and 22.0% of all households were made up of individuals. The average household size was 2.64 and the average family size was 3.07. The median age was 40.0 years.

The median household income was $47,697 and the median family income was $66,561. Males had a median income of $45,270 and females $33,353. The per capita income was $25,023. About 4.5% of families and 7.2% of the population were below the poverty line, including 8.5% of those under age 18 and 6.3% of those age 65 or over.

Dearborn County Racial Composition

Race	Num.	Perc.
White (NH)	47,319	93.37%
Black or African American (NH)	292	0.6%
Native American (NH)	66	0.13%
Asian (NH)	211	0.42%
Pacific Islander (NH)	9	0.02%
Other/Mixed (NH)	2,058	4.06%
Hispanic or Latino	724	1.43%

The county government is a constitutional body, and is granted specific powers by the Constitution of Indiana, and by the Indiana Code.

County Council: The county council is the legislative branch of the county government and controls all the spending and revenue collection in the county. Representatives are elected from county districts. The council members serve four-year terms. They are responsible for setting salaries, the annual budget, and special spending. The council also has limited authority to impose local taxes, in the form of an income and property tax that is subject to state level approval, excise taxes, and service taxes. Board of Commissioners: The executive body of the county is made of a board of commissioners. The commissioners are elected county-wide, in staggered terms, and each serves a four-year term. One of the commissioners, typically the most senior, serves as president. The commissioners are charged with executing the acts legislated by the council, collecting revenue, and managing the day-to-day functions of the county government.

Court: Dearborn County's courts consist of a Circuit Court, presided over by the Honorable James Humphrey (shared with Ohio County in the only such arrangement in the state) and two Superior Courts, the Honorable Jonathan Cleary, presiding over Dearborn County Superior Court No. 1 and the Honorable Sally McLaughlin, presiding over Dearborn County z Superior Court No. 2. Judges are elected to six-year terms. Lawrenceburg also has City Courts, presided over by the Honorable Joseph R. Johns. The Lawrenceburg City Court Judge serves a four-year term.

County Officials: The county has several other elected offices, including sheriff, prosecuting attorney, coroner, auditor, treasurer, recorder, surveyor, and circuit court clerk. Each of these elected officers serves a term of four years and oversees a different part of county government. Members elected to county government positions are required to declare a party affiliation and to be residents of the county.

Dearborn County is part of Indiana's 6th congressional district; Indiana Senate district 43; and Indiana House of Representatives districts 55 and 68.

United States presidential election results for Dearborn County, Indiana

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2020	19,528	76.78%	5,446	21.41%	460	1.81%
2016	18,113	75.06%	4,883	20.24%	1,135	4.70%
2012	15,394	68.86%	6,528	29.20%	434	1.94%
2008	14,886	67.00%	7,123	32.06%	208	0.94%
2004	14,231	67.87%	6,596	31.46%	142	0.68%
2000	11,452	64.88%	6,020	34.11%	178	1.01%
1996	8,318	50.60%	6,269	38.13%	1,852	11.27%
1992	6,974	44.80%	5,116	32.86%	3,477	22.34%
1988	8,195	61.57%	5,066	38.06%	48	0.36%
1984	9,149	64.74%	4,920	34.81%	63	0.45%
1980	7,467	56.36%	5,135	38.76%	647	4.88%
1976	6,176	49.04%	6,348	50.40%	71	0.56%
1972	7,689	64.69%	4,137	34.81%	59	0.50%
1968	6,208	48.65%	4,842	37.95%	1,710	13.40%
1964	5,473	41.47%	7,699	58.33%	26	0.20%
1960	7,619	54.99%	6,216	44.87%	19	0.14%
1956	7,189	56.40%	5,535	43.43%	22	0.17%
1952	7,091	54.82%	5,810	44.92%	33	0.26%
1948	5,353	46.70%	6,040	52.70%	69	0.60%
1944	5,487	51.32%	5,157	48.24%	47	0.44%
1940	5,908	49.29%	6,038	50.37%	41	0.34%
1936	4,669	41.48%	6,366	56.56%	221	1.96%
1932	4,716	41.83%	6,429	57.02%	130	1.15%
1928	6,334	58.49%	4,459	41.18%	36	0.33%
1924	4,588	48.11%	4,330	45.41%	618	6.48%
1920	5,159	50.66%	4,884	47.96%	140	1.37%
1916	2,318	42.18%	3,010	54.78%	167	3.04%
1912	1,366	25.93%	2,957	56.13%	945	17.94%
1908	2,520	41.81%	3,365	55.83%	142	2.36%
1904	2,588	42.99%	3,264	54.22%	168	2.79%
1900	2,533	42.00%	3,371	55.89%	127	2.11%
1896	2,714	44.75%	3,313	54.62%	38	0.63%
1892	2,274	39.20%	3,397	58.56%	130	2.24%
1888	2,648	42.25%	3,531	56.33%	89	1.42%

• Interstate 74
• Interstate 275
• U.S. Route 50
• U.S. Route 52
• State Road 1
• State Road 46
• State Road 48
• State Road 56
• State Road 62
• State Road 148
• State Road 262
• State Road 350

• Nick Goepper professional slopestyle skier, three-time winter Olympic medalist
• Erwin "Cannonball" Baker, motorcycle and auto racer, 1989 inductee in Motorsports Hall of Fame of America
• John Whiteaker, first state Governor of Oregon from 1859 until 1862 and Oregon's Congressman from 1879 to 1881
• Jim Lyttle, professional baseball player
• Lonnie Mack, influential guitar soloist of early rock 'n' roll
• Louis Skidmore, architect that co-founded Skidmore, Owings & Merrill

• National Register of Historic Places listings in Dearborn County, Indiana

• Official website

39°09′N 84°59′W / 39.15°N 84.98°W / 39.15; -84.98